R. & M. No. 2834
(13,9e~)
A.R.~. Technical Re~oz~
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MINISTRY OF SUPPLY
A E R O N A U T I C A L RESEARCH C O U N C I L
R E P O R T S AND M E M O R A N D A
i
Towing-Tank Tests on a
Large Six-Engine Flying Boat Seaplane,
to Specification io/46 (Princess)
PART II
Porpoising Stability, Spray and Air Drag Tests, with
Improved Step Fairing, Afterbody Design and
Aerodynamic Modifications
A. G. SMITH, B.Sc., D.I.C., D. F. WRIGHT A N D T. B. OWEN,M.A.
Crown Copyright Reserved
LONDON : HER MAJESTY'S STATIONERY OFFICE
I954
VRICE. 8S 6d NZT
:Li
Towing-Tank Tests on a Large Six-engine Flying Boat
Seaplane, to Specification o/46 (Princess)
PART II*
Porpoising Stability, Spray and Air Drag Tests, with Improved Step Fairing,
Afterbody Design and Aerodynamic Modifications
A. G. SMITH, B.Sc., D.I.C., D. F. WRIGHT and T. B. OW~N, M.A.
COMMUNICATED BY THE PRINCIPAL DIRECTOR OF SCIENTIFIC RESEARCH
MINISTRY OF SUPPLY
(AIR),
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Reports ,2~d Memora#d~ No. 2 8 3 4"*
November, 19 5 o
Summary.
Introductory.--Further model tests were made on the Princess flying boat to :-(a) improve the main-step fairing in order to reduce air drag while retaining satisfactory porpoising stability at
high water speeds,
(b) reduce the mid-planing porpoising instability found with the hull lines tested in Part I of this report (R. & M.
2641),
(c) test the effect of increased wing and tailplane areas,
(d) predict more accurately the full-scale performance of the final hull form by representing more closely the
anticipated full-scale conditions of lift, slipstream and damping in pitch.
The tank tests were made in sheltered water conditions in the Seaplane Towing Tank, Royal Aircraft Establishment,
Farnborough, oil a dynamic model, and parallel tunnel tests on the step-fairing design were made in the Saro Wind
Tunnel at Osborne.
The final hull form evolved is used for the first production aircraft.
Condusions.--(i) The hull air drag has been reduced about 12 per cent, so ttiat the surface-drag coefficient is of the
order of 1 . 2 5 times that of the equivalent body of revolution of the same length and maximum cross-sectional area.
It is anticipated that this drag reduction will be achieved full-scMe. By adopting more drastic revision of hull fairings,
a total reduction of the order of 25 per cent might be possible, but it was decided that insufficient evidence existed at
the time to justify confidence in resulting hydrodynamic performance at high speeds.
(if) There is evidence of skipping instability on the model at high speeds immediately prior to take-off, or following
landing, but this is probably the result of blister interference with tile sides of the lower pressure circle aft, and therefore
likely to bemuch reduced full-scale. Afterbody clearance from the forebody wake is very good up to at least 340,000 lb
for take-off and 280,000 lb for landing.
(iii) The technique devised for better representation of full-scale lift and slipstream proved successful and enabled
more accurate prediction to be made of full-scale performace. With the enlarged wing and tailplane the stability and
trim on the water are now good by present standards up to at least 340,000 Ib for take-off and 280,000 lb for landing.
These weights are 30,000 lb more than predicted from the tests reported in R. & lVi. 26411, and are above the anticipated
overload design weights.
* Part I, R. & M.2 ~ 1 .
** R.A.E. R e p o r t 4 0 4 , received 28th April, 1951.
(6t785)
t-
(iv) Spray clearances are only slightly improved at the wing and propellers, but little propeller damage is anticipated
up to the above weight limits and none if steel propellers be used. Propeller impact can be reduced by throttling the
middle engines during fast taxying, and flap impact by not lowering them below 60 knots. The final tailplane position
is well clear.
(v) No appreciable improvement in mid-planing stability was obtained by detailed afterbody design. The major
difficulty is still lack of damping in pitch, which could be increased by increasing the dead-rise at the aft step, but not
enough to make the modification worth while at the stage of construction reached.
1. !~troductio~.--Further tests have been made on a dynamic model of the Pri~cess flying
boat to examine the effect of revised aerodynamic and hydrodynamic design on the porpoising
stability, trim and spray. These tests follow on those reported in Part I of this report and include
tile calm-water tests on the final form, used for the first three production aircraft. These tests
were made in the Royal Aircraft Establishment Towing Tank and in the Saro Wind Tunnel
between May, 1947 and August, 1948.
The changes in design from that reported in R. & M. 26411 are : - (a) improvements in main-step fairing to reduce air drag while retaining satisfactory
porpoising stability at high speeds on the water,
(b) a re-design of the wing and power plant installation, on account of a change in design,
resulting in a considerable increase in wing area and propeller thrust. An increase in
the tailplane area and height above the water was also found necessary.
An attempt was made to obtain a closer representation of the anticipated hill-scale lift
characteristics, and also to improve the porpoising stability at mid-planing speeds, i.e. 60 to
80 knots, b y detailed revision of the afterbody design. Such revision is, however, seriously limited,
because the critical factor is the breadth required above the chines for the lower pressurisation
circle of the hull, as was demonstrated in the first series of tests 1.
1.1. Descriptio~ of Flyi~¢g Boat a~¢d Hull Li~es.--The overall design is basically similar to that
described in R. & M. 26411. The final general arrangement and hull lines evolved as a result of
the present tests are illustrated in Fig. 1 and 2.
Leading dimensions and particulars of centre of gravity position and power units are given in
Table 1. In the final form the power units are 10 gas-turbine engines (Proteus) which drive 4
sets of contra-rotating and 2 sets of single propellers. There are three engine installations in
each wing, tile outers* being t h e s i n g l e engines and the middles and inners, coupled engines
driving the contra-rotating propellers. The outer single propeller units are of reversible pitch to
help manoeuvrability at low speeds on the water.
The wing area has been increased from 4,850 sq ft to 5,019 sq ft and the area and height above
the water of the tailplane have also been increased, Table 1. The hull lines have been changed
in the region of the main step where, for the same faired plan form, an elevation fairing of 6 : 1
fineness ratio has been substituted for the 2 : 1 fairing of the original form and also the aft
chine in the same region has been rounded off and faired so as to improve the airflow into the
region below the afterbody bottom, Fig. 3.
2. Details of Tests.--The tests were made in the Seaplane Tank on a 1/28th-scale powered
dynamic model using the same technique as described in R. & ~ . 26411, but were confined to
steady-speed runs with fixed elevator angles in calm water conditions.
* Propeller positions are defined as :-(i) Outers : positions furthest out from hull.
(if) Inners : positions adjacent to hull.
(iii) Middles : positions between inners and outers.
2
2.1. Hull Modifications.--Tests on the effect of modifications to the main-step fairing and afterbody lines on porpoising stability and trim were made first in the model condition, Mod. T,
used for the final tests described in R. & M. 26411, but with the larger raised tailplane for the latter
half of the tests. The tests were made at all-up weights of 310,000 lb and 340,000 lb with the
c.g. at 30 per cent S.M.C. (standard mean chord) with full anticipated take-off thrust but zero
wing flaps. The higher all-up weight tested represents a severe over.loading condition due to the
original smaller wing being used, but was deliberately chosen so as to amplify any deterioration
in the hydrodynamic behaviour caused by the main-step and afterbody modifications.
In parallel with these tank tests, the firm and R.A.E. jointly made comparative tests on a hull
in tile firm's wind tunnel, both to explore the nature of the airflow round the step, and to measure
the. drag with various degrees of fairings and elimination of the afterbody chine ill the main-step
region.
2.2. Wing and Power Plant Modifications.--Following the decision on a final fairing design,
a new model was constructed incorporating the increased wing area and propeller thrust as well
as the f n a l hull form, and the larger tailplane introduced d u r i n g the fairing modification was
retained. Measurements of lift and thrust were made on the model, and wing leading-edge slats
were designed and fitted to improve the lift-slope and stalling characteristics. The model was
now representative of the three prototype aircraft under construction and, besides comparative
tests on the effect of the increased wing area and propeller thrust, a range of weights, c.g. positions
and flap angles were covered to assess the final form performance. The test programme covered
was as tabulated below.
.
Condition
Take-off
All-up
weight
Oh)
Flap
setting
(deg)
310,000
0
15
30"2
24"8
30"2
340,000
0
15
30.2
30-2
370,000
0
30.2
220,000
0
45
28"2
28"2
0
45
28"2
24 "8
28 "2
Landing
250,000
280,000
C.G. position
(per cent S.M.C.)
28"2
The maximum take-off and landing weights tested are considerably greater than any anticipated
overload, but were used to give some systematic data from which the performance characteristics
at other weights could be interpolated as required. The spray impact positions were noted and
plotted in terms of attitude and speed, and photographs were also taken from forward at speeds
below the hump speed (50 knots), to illustrate spray interference with the propellers.
3. Model Wing-Lift and Propeller-Thrust Characteristics.--3.1. Power Units.--The new wing
and power-unit installation is illustrated in Fig. 4. It was decided to make a scale representation
of the contra-rotating and single propeller units, so t h a t the best representation of full-scale
slipstream velocity and twist and their effects could be obtained. The simplest solution available,
3
(61785)
A2
consistent with keeping down the weight for the light load take off test condition, was to use in
each wing a four-stage axial-flow turbine" driven b y compressed air and to couple this by suitable
shaft drive, reduction and bevel gearing to the propellers. These units proved comparatively
easy to manufacture and gave very few mechanical difficulties in operation, as well as providing
a considerable margin of reserve power.
The four-stage axial-flow-turbine was mounted perpendicular to the chord-line along the
position of maximum thickness of the wing. Each complete assembly* was mounted on a stiffened
metal base-plate so t h a t it formed an independent unit which could be removed for maintenance
purposes, and also strengthened the wing. Each unit weighed 11½ oz and the turbine had a
maximum power output of about 1.5 h . p . The propellers were made of cedarwood and were
equivalent to 17 ft diameter full-scale.
This powered model, when balanced to the correct c.g. position was too heavy to represent the
lighter landing conditions, due to the increased weight of the power units compared with the
simpler units used in Ref. 1. An additional wing was therefore made, similar in shape to the takeoff wing, but which had no power unit or propellers fitted and was provided with full-span
leading-edge slats.
3.2. Wi~zg-Sectio~¢ and Lift Measure~ents.--The wing section used on the first dynamic m o d e l 1,
i.e., NACA 6418, at the root chord, did not give the anticipated full-scale characteristics of the
high-speed section actually used on the aircrafh Both the maximum lift and the lift slope
without s]ipstream were much below those obtained in R.A.E. wind-tunnel tests a at a Reynolds
number of 7 × 105. The new wings were therefore made with the actual full-scale section and
leading-edge slats added. These were beaten out of light alloy sheet to the same contour as the
leading edge of the wing. Much better agreement with the anticipated full-scale lift characteristics was obtained. The results of the measurements without slipstream are given in Fig. 5,
and with slipstream in Fig. 6.
3.3. Pr@eller Thr,tst.--The estimated full-scale values of propeller and jet thrust are given
in Fig. 7. The model thrust was calibrated against the turbine inlet pressure over the take-off
speed range and a curve of the pressure required to give the scale propeller thrust deduced.
This was then used throughout the tests. A check on the propeller speed showed that it was
within 5 per cent of the value scaled down from full-scale, so the rotation as well as the intensity
of t h e slipstream should have been correct.
4. Aerodyna~ic and Hydrodynamic Tests o~ Hull-St@ Fairing Desig~¢.--4.1. Air Drag of
Modification N Hull Form.--Wind-tunnel tests were made in the Compressed Air Tunnel of the
National Physical Laboratory to check the aerodynamic cleanness of hull form Nod. N, Fig. 3
of Ref. 1. The results are plotted in Fig. 8 in the form of drag coefficient per unit surface area
against Reynolds number and compared with the results of another series of tests showing what
gains might be expected with a classical form of British hull (designated the basic form) by
degrees and styles of main-step fairing. The Mod. N hull was disappointing, its aerodynamic
cleanness being of the same order as t h a t of a normal hull of similar plan fineness ratio with an
unfaired V plan-form step, although there was apparently a more favourable scale effect.
Examination of the hull suggested that the high drag might be due to : - (a) insufficient step fairing in elevation and plan
(b) flow across the pronounced flared out chines in the forebody
(c) interference at the intersection of the upper and lower pressure circles
(d) the forward cabin.
The first was the most probable source of drag, the elevation fairing at the step on Mod. N being
about 2 to 11 contrasted with a minimum of 6 to 1 found necessary b y tunnel tests to remove
most of the step drag (Fig. 8). The water lines in the main-step region also showed major
discontinuities (see Fig. 3) because of the earlier decision to retain a sharp afterbody chine almost
* There was one unit in each wing consisting of a turbine with its drive to two sets of contra-rotating propellers and
one single propeller (Fig. 4).
4
into the forebody chine ; and a breakaway was to be expected in this chine area, where the air
flows round the step to fill the space beneath the afferbody. These deductions were proved to
be correct b y wind-tunnel drag and tufting tests with various step fairings made in the firm's
wind tunnel, Fig. 9.
It is possible t h a t the flared out chines forward do account for an increase of the total hull
drag up to 3 per cent of the equivalent body of revolution, but no measurable difference could be
found in some unpublished full-scale flight tests made on a Sefford I four-engined flying boat
with and without fairing to the flared out chines.
The effect of filling in the intersection of the upper and lower pressure circles of a ' double
b u b b l e ' or figure-of-eight hull section was tested in the Royal Aircraft Establishment No. 1,
ll½-ft Wind Tunnel, but negligible difference was found at a Reynolds number of 8 × 106.
Similarly, wind-tunnel tests show little drag penalty can be expected for the forward cabin
position full-scale, when boundary-layer transition is forward.
4.2. Wi~d-Tu~ml Tests to Improve Hull-Step Fairi~g.--Tests on a hull without wings or tail
assembly were made in the ' Saro ' Open-Jet Wind Tunnel at 0 deg keel incidence at a Reynolds
number of 4.1 × 106 (based on hull length) with various degrees of fairing, retaining the basic
plan-form of step. The drag results are given in Fig. 8 where they are superimposed on the results
of tests made in the Compressed Air Tunnel at the National Physical Laboratory on a series of
step shapes and fairings. Photographs indicating the flow past the step as shown by tufting
are given in Fig. 9.
The original form, Mod. N, showed possible flow separation both near the keel, where the
elevation fairing was only twice the step depth, and near the chines following the water-line
discontinuity produced by the forward extension of the afterbody fairing. The R.A.E. fairing,
Fig. 9, gave a drag reduction of 14.5 per cent by increasing the step elevation fairing to 8 times
the step depth, and rounding the afterbody chine in the main step region. The firm compromised
on this and obtained a drag reduction of 10½ per cent using a 6 • 1 step elevatioil fairing,
retaining more of the aft chine discontinuity and inserting a shallow cove at the step, Fig. 9.
Further combined R.A.E. and firm's tests in the Saro wind tunnel showed that all signs of
breakaway could be eliminated by rounding the sections on the R.A.E. fairing, so as to fill in the
fairing aft of the step towards the chines, keeping buttock lines straight to as near the chines as
possible to reduce the ' waist ' otherwise found in this region. The first tests (Fig. 9), indicated
t h a t the problem was to merge good buttock lines at the keel region into good water lines in the
•chine region, so that the air could flow round the hull above the step and down underneath the
afterbody. Modifications II and U I on Fig. s show what could be achieved b y doing this, the
basic f.airing/step depth ratio being 8 : 1 in Mod. n and 10 : 1 in Mod. III.
There were no
coves m these modifications.
A comparison of the Saro tunnel and Com)ressed Air Tunnel results at a Reynolds number of
4. ! × 106 follows.
Saro Tunnel
Compressed Air Tunnel
Primess Hutl
Basic Research Hull
Condition
C~
Condition
Cs
Original
Fairing Mod. N 2 : 1 at keel
0.00477
0.00500
R.A.E.
Step fairing Nod. AD 8 : 1
at keel
Saro intermediate fairing ~od.
AE 6 : 1 at keel
Straight fMring, 8 : 1 at keel,
extended towards chines
Ditto with cove
Straight fairing 10" i'at ke'e'l
extended towards chines
0.00406
Transverse step, no elevation
faking
Faired plan-form step, no
elevation fairing
F a k e d plan-form and elevation
main step
Transverse step and straight
fairing
Mod. I
Mod. I I
Mod. II
Mod. III
0.00426
0.00380
0.00386
0-00365
5
Basic streamline shape
..
0.00440
0.00408
0.00383
0.00333
The absolute values of the Saro measurements were in all cases lower than those of the N.P.L.,
as demonstrated by the tests on Mod. N in the two tunnels, but the decreases in drag with
improvement of step fairing were consistent with the N.P.L. systematic results and consistent
with the diagnosis that the high drag of Mod. N was due to the short elevation fairing combined
wKh discontinuities near the chines introduced by the forward retention of the aft chine.
4.3. Towir~g-Ta~k Tests o~z Improved Step Fairirags.--The interpretation of the tank tests on
the various step fairings is complicated b y parallel changes in tailplane size and position, and
attempts to reduce afterbody interference at medium and high speeds by detail changes in afterbody chine and aft step design. In general, the conclusion is that the use of either the R.A.E.
fairing or an improved form of the firm's Mod. 1 fairing had no adverse effect on the stability at
medium speeds, but undue filling in of the fairing towards the chines caused interference at high
speeds and attitudes (small draft).
The effect of rounding off the aft chine in the main step region to improve afterbody ventilation
and step drag was tried in Mod. U. No deterioration of hydrodynamic performance was found.
The effects
(a) 2 : 1
(b) 6 : 1
(c) the 8
of the three basic fairings,
as in Mod. AF
as in Step 1Kod. I, Mod. AE
: 1 R.A.E. fairing, Mod AD
are demonstrated in Fig. 10 for the take-off configuration at 310,000 lb and 0 deg flap. The
second is basically the same as t h a t tested in the tunnel but with the fairing extended nearer
the chines to improve air drag. There was no appreciable change in.stability between the three
configurations though the limited tests at high speed indicated the presence of a skipping porpoise
just prior to take-off with the larger tairings, confirmed in later tests. This probably also existed
in the Nod. N configuration, but had not been found, occurring as it does within 5 to 10 knots
of the flying region.
The comparison of the fairings at the severe overload take-off condition is given in Fig. 11.
The 2 : 1 fairing was tested in conjunction with the original tailplane while the 6 : 1 and 8 : 1
fairings were tested with the new tailplane. Allowing for the slight deterioration in stability
with the new tailplane (see section 5.2), there is again no appreciable difference in stability
between the three configurations. The high-speed skipping characteristics were not investigated.
The possibility t h a t the extended step fairing was introducing ' s k i p p i n g ' at high speeds
with increased draft, was investigated b y making a series of modifications (Table 2) to the aft
chine clearances and the introduction of a shallow cove at the main step.
The cove was introduced to ensure t h a t the water flow was broken cleanly away from the hull
at the step, but produced no change. Breaker or subsidiary steps were put transversely on the
fairing aft of the main step to separate any main blister attachment at high speeds and these had
the effect of changing the skipping to a gentle pitching motion. Observation, however, showed
t h a t this change was as likely to be caused b y the breaking down of the blister and avoidance
of its attachment to the lower pressure circle above the afterhody, as b y preventing attachment
to the fairing. To reduce the attachment to the lower circle, the afterbody chines were both
turned down and flared out to form an abrupt discontinuity across the path of the main blister
spray of which the direction was almost parallel to the existing chine line. Little gain was possible
because of the restrictions imposed b y the structure of the lower pressure circle.
As a compromise, the final fairing adopted was the 6 : 1 as tested, but with a shallow cove
of plating thickness to ensure separation full-scale.
5. ttydrody~amic Tests o¢¢ Modificatio~s to Aft Step and Tailfllam.--5.1. Modificatio~s to Aft
Step.--Detail changes in the aft-step strength were made in order to t r y and reduce the midplaning porpoising instability at high draft present under certain disturbance conditions 1. The
loss of mid-planing speed stability with increase in draft (load) is often associated with lack of
sufficient damping in pitch and the water loads resulting from the aft-step impacts.
The aft-step dead-rise was therefore increased to about 50 deg by raising the chines from about
half way back on the afterbody to both lessen the hydrodynamic strength and increase the water
damping. The effect was tried with the smaller tailplane of Mod. N and the 8 : 1 main-step
fairing (Table not illustrated) and also with the final large tailplane of Mod AK, with both the
8 : 1 and 6 : 1 step fairings (Figs. 12 and 13). With the 8 : 1 step fairing there is little apparent
change in stability due to modifying the aft step, but with the 6 : 1 fairing, which is the final
design case, Fig. 13 shows that there is a considerable gain in mid-planing stability at both
310,000 and 340,000 lb though apparently with some loss of stability at high speeds. This loss
is probably due to the decreased efficiency of the aft-step chines in breaking away the main blister
spray from the hull sides.
A second modification was to drop the aft keel to produce a dead-rise of the order of 70 deg,
Mod. AG (Table 2, not illustrated), but this was not very effective, possibly because of the contrary
effects of dead-rise and increased local keel incidence.
Reduction of aft-step strength was not considered worth while at the stage Of construction
reached when balanced against the possible loss in efficiency at the hump and high-speed
conditions.
5.2. Modifications to Tailplane.--The tailplane was enlarged in plan form area and raised
for aerodynamic reasons, Table 1. This change produced a small deterioration of porpoising
stability in the mid-planing region, possibly because the improvement in damping in pitch, due
to the increased area, was more than offset by the loss due to the increased height above the
slipstream and ground. The comparison of Mods. AB and AC is shown in Fig. 14 for 310,000 lb.
About 4 deg more up-elevator is required to avoid the lower porpoising limit.
6. Hydrodynamic Tests with Increased Wing Area and [email protected] larger wing and high
thrust engines were tested with the final accepted hull form in modification AK of Table 2. The
water characteristics were greatly improved for the same all-up weight, the improvement in
take-off at 340,000 lb and landing at'280,000 lb being shown in Figs. 15 and 16. This is all due
to the decreased draft, the net effect of the larger step fairing and tailplane being negligible.
The skipping tendency just before take-off is unchanged, but for speeds above 100 knots is
such that any disturbance causes the model to become airborne. Below 100 knots during landing,
at keel attitudes greater than 10 deg, the nose-up and skipping tendencies exist but, as noted in
section 4, may be due to the lower-circle wetting by the main blister.
7. Hydrodynamic Characteristics of Final Form (Mod. AK.)--7.1. Stability and Trim in Take-off
and Landing.--7.1.1. Effect of all-up weight (Figs. 17 and !8).--Deterioration of stability is delayed
to well above 340,000 lb in the take-off condition of mid-planing speeds, Fig. 17. The change from
positive to negative stability is in practice not so abrupt as indicated by the diagrams, it being
a gradual process, but the improvement is likely to be found in wave behaviour 1.
The high-speed instability at high attitudes remains similar at all weights, increasing at higher
speeds with increase of all-up weight.
At attitudes below 10 deg the model flies if disturbed within 5 to 10 knots of flying speed at all
weights. Above 10 deg the model would skip at speeds above 90 knots at all weights, whilst
afterbody lower-circle wetting occurred, but below that speed the instability merges into the
mid-planing speed upper-limit two step porpoising without afterbody wetting.
The lower limit of porpoising instability and the free-to-trim curve rise with increase in weight
in a normal manner.
The stability and trim characteristics in landing, Fig. 18, are very similar in all respects at the
landing-weight range below 250,000 lb and are consistently fair up to 280,000 lb, the maximum
load anticipated.
7
7.1.2. Effect of c.g. position (Figs. 19 and 20).--In take-off both upper and lower limits are
substantially unaltered for the c.g. range 24.8 to 30.2 per cent S.M.C., but the 0 dog elevator
free-to-trim attitude is just below the lower limit at the forward c.g. position. The change in
elevator angle required to compensate for c.g. shift is about 2 deg per 1 per cent S.M.C. shift.
In landing the changes of stability and trim are of the same order.
7.1.3. Effect of wing flaps.--Use of 15 dog take-off flap slightly improves the take-off stability,
probably because of the reduction in draft, Figs. 17 and 21. There is a nose-down change of trim
of the order of 2 dog at high speeds at small elevator angles, but there is ample elevator power
in hand.
The proposed flap for landing, 45 deg, lowers the landing speeds the order of 15 knots and
improves the stability at both upper and lower limits except at high speeds and low attitudes,
Figs. 18 and 22. The lower limit with disturbance is raised just below touch-down speed, probably
the result of the applied nose-down moment. The trim attitude at high speeds is lowered the order •
of 2 deg but there is ample elevator power in hand.
7.2. Spray Clearance in Take-Off.--7.2.1. Displacement @eed ra%~e.--There is considerable
spray interference into the propellers at weights greater than 310,000 lb, the lowest weight
tested for take-off. The most severe speed is around 25 knots and the middle propellers are the
worst hit at all speeds between the pick-up limits of 15 to 35 knots, Figs. 23 to 27 inclusive.
Since propeller damage is roughly proportional to the cube of the rotational speed of the pr0pellerL
the main thrust for high-speed taxying should be supplied by the outers to minimise spray
damage.
7.2.2. Hump and planing regions.--During take-off with flaps up at all weights above 310,000 lb
the wing trailing edge and tail are hit by the main spray in the hump region, the impact on wing,
flaps and tailplane becoming severe above 340,000 lb. The propellers are clear throughout the
hump region. With flaps in the 15 dog position for take-off the spray impact on the tail is
lessened but is more severe on the flaps.
The spray impact at high speed is restricted to high attitudes on both wing and tailplane, and
is of a light nature except possibly at 370,000 lb weight.
8. Interpretation Model to Full-Scale.--& 1. Hull Air Drag.---The reduction of hull air drag, with
the improved step fairing, is of the order of 12 per cent at the Reynolds number of test, 4 × 106
(based on hull length). Full-scale, the cruising Reynolds number is of the order of 200 × 106
and it is not possible to say definitely either that the gain would still be found at this Reynolds
number, or what the absolute drag would be. The C.A.T. tests on the developed hull series
cover tile Reynolds number range 2 to 40 × 10L over which range the different forms have drag
against Reynolds number curves which are nearly parallel but with a slope decreasing at a slower
rate with increase of Reynolds number than that of the turbulent coefficient of skin friction.
The slope for the Princess hull, is however, steeper, and more nearly comparable with that of
turbulent skin-friction. This is probably due in part to a change of technique in producing a
good surface finish which will stand up to C.A.T. operating conditions. Extensive skin-friction
measurements made for ship performance, reported in Ref. 5, show that the skin friction will
follow parallel to the theoretical smooth turbulent value up to Reynolds mlmbers of a much greater
order than t h a t at which the Princess will fly. It is therefore tentatively concluded that the gain
in drag' will hold full-scale and also that the total drag will be the same ratio* of the skin-friction
drag, provided the finish is sufficiently smooth for turbulent-flow boundary-layer conditions to
exist. Since the hull drag is of the order of 15 to 20 per cent of the total drag on a flying boat
* Strictly the ratio changes with Reynolds number and an incremental correction should be made to the theoretical
value, But the ratio gives the right order for the purpose of this analysis.
8
of this class and the payload is small for the extreme ranges considered, the achieved drag redaction is equivalent to the order of 3 per cent increase in range or 15 to 20 p a s s e n g e r s a t the
maximum range.
A larger overall drag reduction of over 20 per cent would be obtainable on this hull form by
using a more extreme elevation step fairing, which has since been shown possible hydrodynamically
full-scale on a Sunderland given some additional ventilation 6. At the time of the model tests,
however, there was some doubt as to the order of improvement to be gained full-scale in
stability at high speed and the compromise of a 6 : 1 fairing was decided upon.
8.2. Stability and Trim.---The porpoising stability is generally good at model-scale up to
weights considerably greater than those anticipated full-scale, but a favourable scale effect is
anticipated in accepting the narrow high-speed skipping and mid-planing instability characteristics present on the model.
The high-speed skipping, if present full-scale, is not likely to be noticed in take-off because
the aircraft would fly off on the first skip, but it might cause one or two skips when landing near
the stall, expecially in waves. However, this apparent skipping is more probably due to the
interference between the main blister from the step and the afterbody lower pressure circle than
the step fairing and, in this case, would llndoubtedly be much less severe if present at all at fullscale. This is a result of the known change of form of the blister from a continuous sheet
model-scale to drops full-scale. For the same reason, if interference does occur at the step fairing
near the chines, this also is less severe full-scale, as illustrated b y the Sunderland tests", provided
the afterbody clearance from the forebody wake is good. In all, skipping is very unlikely to be
found full-scale up to 340,000 lb. Above t h a t reduction of afterbody clearances from the wake
may lead to genuine skipping trouble.
The landing instability found at high speeds is further exaggerated model-scale because of the
model aerodynamic characteristics. At model-scale the dynamic model is free to find its own
trim, but full-scale there can be superimposed a favourable control and throttle movement.
The model when landing would trim very low down after a bounce and land well in the lower
instability range.
The mid-planing instability is only likely to occur in waves which produce a severe enough
disturbance.
The order of pick-up possible in waves will be described in later tests but there should be no
difficulty in sheltered water operation, or in high seas if short. There is also little damping modelscale, a primary cause of the instability on disturbance, but this is generally greater full-scale-as found f~flt-scale on the Seaford 7. These favourable scale effects are, however, only possible
because the afterbody clearance relative to the forebody wake shape is satisfactory 8.
Trim and elevator response is likely to be very similar model and full-scale because of the
fairly accurate representation of slipstream effects".
8.3. Spray Clearances.--Full-scale tests on the Walrus ~° and Seaford ~,11 hav:e shown that the
main spray which appears as a blister of ' green' water model-scale occurs full-scale as a large
number of separate drops. Although the relative amount of water in the main spray would be
the same, it is probable t h a t the slipstream would not lift the broken water as much as tile
continuous blister. Therefore, t h e propeller interference shown in Fig. 22 is probably pessimistic
and full-scale the slipstream would further break up the main spray.
A dense but fine mist was always present full-scale on the Walrus and Seaford above the forward
and main spray, but this caused no structural damage.
9. Conclusions.--The final hull form was developed in the model tests described in this and
the previous report (R. & M. 2641) 1. With the revised step fairing the hull air drag has been
reduced b y the order of 12 per cent and a reduction up to the order of 20 per cent is possible
9
given more freedom to revise afterbody design. It is concluded that the streamline plan-form
step faired in elevation can be designed to have a drag as low as that of a transverse step faired
in elevation and have hydrodynamic characteristics at least as good. To reduce air drag, it is
important to fair in water lines as well as buttock lines and to do this the afterbody chine should
be rounded off in the main-step region.
The effect of a large increase in wing area and slipstream is to improve the porpoising stability
and trim characteristics such that they are very good by contemporary standard at the normal
all-up weights of 310,000 lb for take-off and 240,000 lb for landing and good up to at least
340,000 lb and 280,000 lb respectively. This represents a gain in permissible all-up weight of
the order of 30,000 lb over that with the first wing.
The spray clearances at the propellers and wing are, however, little different because the
favourable effect of increased lift is nullified by the unfavourable higher slipstream velocity.
Greater improvement is, however, possible by throttling the engines driving the middle propellers,
the only ones involved in spray impact in the 25 knots water-speed region. Negligible propeller
damage is expected up to 340,000 lb all-up weight if steel propellers are used. The tailplane is,
in general, well clear of damaging spray as a result of its raised position and the overall decrease
with the larger wing and increased slipstream.
It was not found possible to effect any appreciable improvement in mid-planing characteristics
by detailed afterbody design. Some gain in damping was possible by weakening the aft step
(increase of dead-rise) but not enough to make it worth while.
High-speed wake afterbody interference was examined in more detail and a narrow skipping
unstable range found near take-off and landing speed. This was probably a result of interference
between the main blister from the forebody and the lower pressure circle at small drafts and high
attitudes and would probably have been accentuated if extreme step fairings were used. Nothing
could be done to improve this, @ Ref. 1, because of restrictions imposed by the lower pressure
circle structure. This interference is likely to be much less full-scale. Generally, afterbody
clearance from the wake itself is very good up to 340,000 lb all-up weight for take-off and 280,000 lb
for landing.
Increase of tailplane area and height made the stability characteristics slightly worse. Improvement due to increase in area was more than offset by the loss due to increase in height above the
water.
The technique devised for representing the very intense slipstream on the dynamic model of
this design proved successful, making possible a better assessment of the hull capabilities full-scale.
10
REFERENCES
No.
Title, e~c.
Author
1 A . G . Smith, G. L. Fletcher, T. B. Owei1
and D. F. Wright
Towing-Tank Tests on a Large Six-Engined Flying Boat Seaplane,
to Specification 10/46. Princess. Part I. General porpoising
stability, trim, and spray clearance. R. & M. 2641. January, 1948.
2
D. Llewelyn-Davies, W. Tye and D.
~acPhail
Design and Installation of Small Compressed Air Turbines for
Testing Powered Dynamic Models in the R.A.E.. Seaplane Tank.
R. & M. 2620. April, 1947.
3
A.S. Worral
. . . . . . . .
Wind-Tunnel Tests on a Six-engined Flying Boat (Saunders Roe
10/46) with Slipstream. Aero, Report 2226. October, 1947.
4
J. Allen
. . . . . . . . . .
Full-Scale Spray Tests of a Four-Engined Flying Boat (Seaford) with
Special Reference to Propeller Damage. A.R.C. 11237. December,
1947. (Unpublished.)
Fifth International Conference of Ship Tank Superintendents.
London. H.M.S.O. September, 1948.
5
An Interim Report on the Hydrodynamic Performance of a Large
Four-Engined Flying Boat, Sunderland Mk. V, with a 1 : 16.75
Main-Step Fairing. A.R.C. 12,162. January, 1949. (Unpublished.)
6
J . A . Hamilton
..
7
J. Stringer . . . . . . . . . .
8
K.M. Tomaszewski and A. G. Smith
9
A.G. Smith and H. G. Wbite
Full-Scale W a t e r Stability Tests with Special Reference to Hull
Pounding, SeafordI. A.R.C. 10851. July, 1947. (Unpublished.)
..
..
Some Aspects of the Flow Around Planing Seaplane Hulls or Floats
and Improvement in Step and Afterbody Design. Congress of
Applied Mechanics, 1948.
A Review of Porpoising Instability of Seaplanes.
February, 1944.
R. & M. 2852.
10
D. Llewelyn-Davies and A. G. Smith ..
Model and Full-Scale Tests on the Water Performance of a Small,
Single-engined Amphibian. A.R.C. 12031. (Unpublished.)
11
J . E . Allen . . . . . . . .
Full-Scale Spray and Wake Observations on Seaford. A.R.C. 10348.
November, 1946. (Unpublished.)
11
TABLE 1
Leading Particulars of Flying Boat
Hull
Mod. N
* m a x i m u m b e a m (b) . . . . . . . .
* F o r e b o d y length with respect to point of s t e p
* A f t e r b o d y length with respect to point of step
Counter length
. . . . . .
A f t e r keel angle
..
..
F o r e b o d y dead-rise angle at step
Heel to heel angle
.
..
*Step d e p t h unfaired at keel
Cove d e p t h
. . . . . .
Fairing
. . . . . . . .
*Hull m a x i m u m height
* M a x i m u m radius of u p p e r circles
..
* M a x i m u m radius of lower circles
..
Setting for keel to hull d a t u m
..
16.6 ft
6 3 . 7 It 3.84 b
57.3 ft 3.45 b
2 2 . 0 ft
7 ° 0'
25 ° 0;
8 ° 20'
1.50' = 0.09 b
0-16 ft 0.01 b
Approx. 2 : 1
24.5 ft
5-7 ft
7 . 3 ft
Mod. A K
16.66 ft
6 3 . 7 ft 3.82 b
57.33 ft 3.44 b
26- 67 ft
7 ° O'
25 ° O'
8 ° 20'
1.36' = 0.082 b
0 . 0 3 It
Approx• 6 : 1
24.25 ft
5 . 6 2 ft
0°
7.25 ft
0o
220 ft
4850 sq It
26 ft
11 ft
10
22.05 ft
Low d r a g
N A C A 6418
18% to 12%
0o
2 ° 12'
4 ° 30'
2 ° 0'
209.5 ft t
5019 sq It
30 ft
12 33 It
8" 75
23.97 It
Low d r a g
Low d r a g
18% to 15°,/o
0o
0o
4 ° 30'
4 ° 30'
6 5 . 5 It
870 sq ft
12 °
13-6 ft
77.17 It
1099.62 sq ft
12 °
14.57 ft
2 8 . 9 ft
Wing
Span
. . . .
Area (gross)
..
R o o t chord
..
Tip chord
..
Aspect r a t i o
..
Mean chord
Section full-scaie
i[
Section model-scale
T/C ratio (root chord to tip cl~ord)
D i h e d r a l from root to o u t b o a r d engine
D i h e d r a l from o u t b o a r d engine to t i p
W i n g setting to keel d a t u m full-scale
model-scale
Tailplane
Span
. . . . .
Area (gross) (approx.) i
. . .
Dihedral
. . . . . . . .
Mean chord
Height of tailpiane leading edge at
datum
. . . .
. . . . .
. . . .
..
root alcove hull
25-6 ft
* The small v a r i a t i o n between Modifications N a n d A K are due to the lines h a v i n g been lofted between these
modifications.
t 219.5 ft w i t h floats retracted•
12
TABLE
C.G. p o s i t i o n s (model)
1--continued
•
S.M.C.
(per cent)
Mod. N
Landing'~
Take-offf
. . . . . . .
Mod. A K
i
~. f n o r m a l
. . . .
,anctmg) forward . . . .
Mod. A K
T,
~,f normal
. . . .
aKe-on\ forward . . . .
Distance
from F P
(ft)
Height above
keel datum
(ft)
30
57 "2
20"2
. . . .
. . . .
28"2
24"8
56.55
55.76
19.25
19.25
. . . .
. . . .
30"2
24"8
57.09
55.83
20.34
20.34
. . .
TABLE
2
List of Modifications and their Effects
Nature of Mo.dification
Modification
Aft chine rounded extensively near main step. Aft
U
chine turndown removed to three-quarters back
on afterb3dy length
Step fairing built up in plasticine to about 5 : 1. All
V
chine turndown on afterbody removed and wind
down of dead-rise on afterbody removed
Afterbody chine turndown restored on front half ..
W
Chine flared out on aft half on afterbody. Chine
X
rounded on forward 0.2 afterbody
Afterbody
chine turndown put on in place of flare
Yi
out. Stop elevation fairing altered to give a cove
of about 0.05-in. deep at the step model-scale
Chine
turndown on aft half of afterbody removed ..
Y2
Breaker steps 0"05-in. deep model-scale built up
Ya
transversely on step fairing at various positions
Afterbody chine raised in vicinity of aft step to
Z
increase dead-rise to about 55 deg
R.A.E. 8 : 1 step fairing on Stations 12-21, hull
AA
otherwise to Drg. PD.!33 Issue D
R.A.E. 8 : 1 step fairing. Dead-rise at aft step
AB
increase to 50 deg by warping
R.A.E.
8 : 1 step fairing. Aft step dead-rise 50 deg.
AC
Larger tailplane fitted in raised position
R.A.E. 8 : 1 step fairing. Afterbody aft of Station
AD
22 as per firm's offsets, (AA). Larger tailplane
Saro 6 : 1 step fairing fitted . . . . . . . .
AE
Step fairing 2 : 1 as Mod. T and larger tailplane ..
AF
AG
AH
AI
aJ
AK
Aft-step keel dropped, chines fixed, to give dead-rise
of 7 deg at aft step
As AG, but step fairing increased to 10 : 1 and fairing
buttock lines kept straight from keel to 50 per cent
beam
Saro step fairing 6 : 1, aft step as AB
....
Secondary aft step introduced at 0.7 aft on
afterbody
Saro 6 : 1 fairing with final hull lines (AE). Increased
wing area and slipstream
18
Effect of Modification
No change from conditions of Mod. T (final form of
Part I), which form is original of this report
No change in mid-planing speed stability.
speed attitude skipping found
High-
No change
No change in stability
No change in stability
No change in stability
High-speed skipping altered to simple pitching
with little heave
Small gain in stability at mid-planing speeds
No change in stability from Mod. T
No change in stability from Mod. T
Slight deterioration in stability
No change from AC
No change in stability
No change in stability, but slightly worse than
Mod. T because of raised tailplane
No change in stability
No change in stability
No change in stability
No change in skipping stability
Mid-planing instability eliminated, but no change
in high-speed skipping
\\
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14.8'
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FIG. 1. General arrangement of 10/46 final form (Mod. AK).
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FIG. 2. Hull lines of 10/4@ for 1/282h-scale dynamic model final form (N[od. AK).
MODEL
DIMENSIONS
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FIG. 7.
Propeller and jet thrust for take-off, full-scale.
FIG. 8. Effect of main-step and chine fairings on hull air drag. Basic hull
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R.A.E. 8 : 1 step fairing
•
?
.
.
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• i_
Firm's 10: I step fairing
]ZIG. 9.
Airflow photographs of three main-step fairings tested in 5aro Wind Tunnel
at hull Reynolds number ----- 4 × 10 e.
20
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-
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.
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: HIGH ATTITUDE
I AND SPEEDS
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20°
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ANb SPEEDS
rt:cP
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70
80
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SPEED KNOTS FULL SCALE
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O
.50
4-
MOD AE
G I FAIRING
NE.~ TAILPLANE
-4
Z
70
80
~
IOO
SPEED KNOTS FULl. SCALE
'110
FIG. 10. Effect of main-step fairing modifications on stability and trim.
Take-off at 310,000 lb. Flaps 0 deg. C.G. normal, 30.2 p e r c e n t S.~.C.
New tailplane.
4O
c
~:1 I~AE FAI~ING
NEW TAILH_ANE
-2
o
60
'~"
MOO AD
•
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\
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g
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D
AE
G~I FAIRING
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130
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~IOH ATTITUDES
AND SP£EOS
-I~_
~: ' 2 ° °
. t20
FULL SCALE
t4NOT TESTE(~.AT
HIC.~ ATTITUDES
AND SPEE.DS
&'° + \
FAIRING
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5O
GO
70
80
90
SPEED- KNOTS FULL SCALE
IOO
lid
4O
50
GO
70
SO
.~0
I00
I I0
•+SPEED- KNOTS FULL SCALE
FIG. 11. Effect of main-step fairing modifications on stability and trim.
Take-off at 840,000 lb. Flaps 0 deg. C.G. normal, 30.2 per cent S.M.C.
'+'
,+_-, SKIPP[NG WHEN DISTURBED
E} ,SV-JPPINGWITHOUT Di.E'i'URBANCE
FLEW WHEN DISTURBED
STABILITY LIMITS
+ STABLE
e, JUST 5TABLE WHEN DISTURBED
:4~ UNSTABLE WHEN DISTURBED
~) UNSTABLE WITHOUT DISTURBANCE
STABLE
~:i
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~)
UNSTABLE WHEN DISTURBED
FLEW WHEN DISTURBED
UNSTABLE WITHOUT DI`BTURE~kNCE --STABILITY LIMITS
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SKIPPING WITHOUT DISTURBANCE
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MOIl AI
AFT STEP bEADRtSE 50 °
r
50
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MOD NO.
AFT STEp DF.,ADRISE500
,?.
~,o°
o~
4-
70
80
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SPEED - KNOTS FULL SCALE
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SO
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r
70
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`90
100
SPEED - KNOTS FULL SCALE
70
80
90
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NOT TESTE~ ,~
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AND SPE£DS
'
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f
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70
80
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S E E D - KNOTS FULL SCALE
GO
A L L UP WEIGHT 3 1 0 , 0 0 0
LB.
A L L UP WEIGHT= 3 1 0 , O O O L B .
14-
14.
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NOT
AT HIGH
ATTEUDE
&SPEED
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70
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AFT 'STEPOEADRISE NORMAL
AFT STEP.DEADRISE 50 °
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AFT STEPDEAORISENE~MAI,
f
•
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lid '
•SPEED- KNOTS FULL SC~.LE
LB,
FIG. 12. Effect of increased aft-step dead-rise on stability and trim.
Take-off. Flaps 0 deg. C.G. normal, 30"2 per cent S.M.C.
8 : 1 main-step fairing. New tailplane.
o
50
GO
.I
70
80
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rOD
SPEED- kNOTS FULL SCALE
ALL
l
IIQ
50
GO
UP WEIGHT 3 4 . 0 , 0 0 0
I
70
80
,90
IOO
SPEED- KNOTS FULL SCALE
IlO
LB
FIo. 13. ]Effectof increased aft-step dead-rise on stability and trim.
Take-off. Flaps 0 deg. C.G. normal, 30.2 per cent S.I~I.C,
6 : I main-step fairing. N e w tailplane.
÷
+~
K÷~
I~
STABLE
JUST STABLE WHEN EIISTURBEO
UNSTABLE WHEN DISTURBEO
IJNSTABLE WITHOUT DISTURE~ANCE
SkiPPING WHEN DISTURBED
,SKIPPING WITHOUT DISTUR~NEE
FLEW WHEN DISTURBEO
.STABILITY LIMITS
\ "÷
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o ~ I0
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~=-fo°
~,-io°
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ORIGINAL TAILPLAINE
d
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GO
70
80
SO
I00
~PEED- kNOTS FULL' `SCALE
MOO, AC
NEW TAILPLANE.
J
I10
O
t
60
70
80
SO
IOC}
SPEED- KNOTS FULL SCALE.
rio
FIG. 14. Effect of increased tailplane area and height on stability and trim.
Take-off at 310,000 lb. Flaps 0 deg. C.G. normal, 30.2 per cent S.M.C.
8 : 1 main-step fairing.
23
+
@
STABLE,.
JUST STAt~LE ~W4EN DISTURBED
FLEW WHEN DISTURBED
Ui:,4STABLE WHEN DiSTuRBED
-i-
b'ITNQIJ'I' DISTURBANC..E
UNSTABLE
÷
+)
SKIPPING WNEN DISTURBED
SKIPPING WI'TNOUT DISTURBANCE
STAB,I!..ITY LIMITS
--
STABLE
~
SJ<IPPtNGWNEN DISTURBED
JUST b-'I"ABLE WHEN DISTURBED
8]
SKIPPINGWITHOUT DISTURBANCE
~,-~ UNSTABLE WH.EN DISTU#BED
FLEW WNEN DISTURBED
G
STABILITY LIMITS
UNS'[ABLE WITH,OUT DISTURBANCE.
t4
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IZ
IZ
/ 4"~
8
ID
/
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...+. ~ ' +
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~:-zo
l
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s
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n
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2,
0
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2.0
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N
40
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70
80
~
SPEED- KNOTS FULL SCALE
IOO
lid
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O
150
/-*~----2
---4
-.
~
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20
so
2
B
-,,.:>
,+
I --
~
7o
8o
so.
log
'-~' "~°°
'~ "°°
-
OF REPORT,
C.G.
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lid
150
- •
30°,15
.S.M.C.
\\%
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S
/
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8.
./
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,5o
14
i
Ul
0
40
MOD. N. ORIGINAL F O R M
iX
/
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S.M.C.
•, -6,l
I0
0
SPEED- kNOTS FULL SCALE
ORIGINAL FORM OF REPORT. C.G. 3 0 %
14.
I-9
m
0
~.
4-
d
/_\
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s
\
\
X
~..... ~,
/
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.,,.\
d
a
J.
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%=O°
z
z
0
O
IO
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MOD. AK.
Fig. 15.
40
FINAL
SO
GO
70
80
90
SPEED - KNOTS FULL SCALE
FORM
OF REPORT.
IOO
110
120
ISO
0
"o
I0
50
MOD. AK.
C.G. 30-2°/o S.M.C.
Effect of increased wing area and slipstream on stability
and trim. Take-off at 340,000 lb. Flaps 0 deg.
2-0
FIG. 16.
40
FINAL
50
Co
70
80
90
SPEED- KNOTS 'FULL SCALg
FORM
1(30
lid
120
150
OF REPOR"£ C.G, 2 8 " 2 ° / ° S.M.C.
Effect of hacreased wing area and slipstream on stability
and trim. Landing at 280,000 lb. Flaps 0 deg.
@ STABLE
I~1 E~<IPPING WHEN I~s'ruRE:ED
~" 3Ub-"r STABLE ~ E N
DISTURBED
SKIPPING WITHOUT DISTURBANCE
~,~ UNSTABLE WHEN DISTURBED
(~
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UNSTAEILF.. WITHOUT DISTURF',ANCE
FLEW WHEN DISTURBED
STAe,ILI$~' LIMITS
14
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30
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70
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SPEED - Ki~OT~
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ALL
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tOO
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70
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80
i
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lid
120
130
FULL S C A L E
ALL UP WEIGHT:340,O00 13
14
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70
80
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S P E E D = kNOTS
FULL SCALE
IOO
liD
r?.o
I;~o
" "
ALL .UP WEIGHT=370jO00 LB.
FIG. 17. Effect of all-up weight on s t a b i l i t y a n d t r i m of final form, Mod. A K .
,, Take-off. F l a p s 0 deg. C.G. normal, 3 0 . 2 p e r cent S.?¢I.C. .
.: ; U
,5
+
STABLE
.TUBT STABLE WHEN DISTURBED
~KtPPIN~ WHEN DLSTURBED
.SKIPPING WITHOUT DISTURBANCE
UNSTAI=~LE W H E N
FLEW WHEN DISTURBEO
(~
DISTUI:IR~ED
tJINSTABLEWITHOUT DISTURBANCE
LIMIT5
STABILITY
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e,o
•.SPEF..I~- kNOTS FULL $~7.~LE
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ALL
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Ioo
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120
l~O
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%
14
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4
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20
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50
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70
80
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SPEED - KNOTS FULL SCALE-
ALl
UP WEIGHT = 2 5 0 , 0 0 0
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150
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LB
14-
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1,9
to
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121
-r
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20
50
40
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@0
tO0
II0
i20
i:tO
SPEED- .I'C~OT8 FULL ,SCAL.E
A L L UP W E I G H T ;
280,000
LB
FIG. 18. •Effect of all-up weight onstability and trim of final form, Moc1.AK.
Landing. Flaps 0 deg. C.G. normal, 9,8.2 per cent S.M.C.
'26
•+
Si"A~..E
(~
(~
3"UST STABLE WHEN DISTU~BF-,,D
UNSTABLE WHEN DtSTUR~F..D
UNSTAt~..E WITI"IOUT ~ S T U R I ~ C E
+ STABLE
,-~ ..,'UST STABLE ~/HEN DISTURBED
UNSTABLE WHEN DISTURBED
UNSTA{SLE WITHOUT DISTUR~NCE
SKIPPING WH&'4 DISTURBED
SKIPPING WITHOUT DISTURBANCE
FLEW WHEN DISTURL,ED
STABILITY LIMITS
m
I'TL4 SKIPPING WHEN DISTURBED
E~ SKIPPING WITHOUT DISTURBANCE
FLEW WHEN DISTURBED
- STABILITY LIMITS
14.
u~
.
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m 16
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4O
5O
6O
,SPEED - KNOTS
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24.BZ
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7O
80
FULL SCALE
E30
IIO
I?O
(0
3b
~0
4O
150
S.MC.
50
GO
.SPEED - kNOTS
e.G.
24'8
70
80
FULL SCALE
°/o
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IOO
IIO
1'20
150
IIo
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130
S.ME.
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,SPEED- KNOTS
C.G.- 3 0 . 2
FIG. 19.
70
80
~'ULL SCALE
~O
I00
IIO
I~0
I~O
O
°/o S.M.C.
Effect of c.g. shift on stability and trim of final form, Mod. AK.
Take-off at 310,000 lb. Flaps 15 deg.
Io
2.o
~o
4-0
50
G40
70
BO
SPEED- KNOTS FULL .~CALE
C.G = 2 8 2 °/o
FIG. 20.
~o
IOO
S.M:C
Effect of c.g. shift on stability and trim of final form, Mod. AK.
Landing at 250,000 lb. Flaps 45 deg.
"I',' 1' ~" !1' -,:F S'IABLF-..-, " . . . .
--~ ..Y0"ST''STAB'L¢'~ WHEN IDIITORII~.B
~; UNSTA~:~_E WREN DI~ruRIIED
UNST,ABI~E~' "~/ITEIOUT DIS:'[u~EtANCE
14
-
/I ~
i '°
+
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UNSIABLE WITHOUT DISTURBANCE
~ SKIPPING WHEN DISTURBED . . . . . . . .
" "1~ SKIPPING WITHOUTD{b-I'URBANI:£ . . . . .
- .
FLEW WHEN Dib-'fURBED
*
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14
I
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/
8
9
p~
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.
.
.
.
~ GLI$TSTABLE, WHEN D I S T ~ D
~-~ UNSTABLE WHEN Dg~IXJRBED
I
_ +X% ~
t~
. . . . .
-- "
~:~ .SKIPPING WHEN DISTURBED
SKIPPING WITHOUT DIST0,~BANCE
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" ~
STABILITY LIMITS
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SEED- KNOTS
70
8O
FULLSC,.~LE'
~3
IOO
I10
" tZO
130
O
10
LZO
;30
40
50
60
SPE~D- kNOTS
70
80
A L L u p W E I G H T =' 2 2 0 , 0 0 0
ALL UP WEIGHT 310,OOO LB.
=
_~O
I00
110 " IZO
FULL S C A L E
I~O
" "
LB.
14
14
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IZ
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k
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40
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GO
70
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I~O
150
FULL SCALE
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IQ
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~
40
50
SPEED-
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KNOTS
70
80
.~O
1OO
lid
IPO
I~0
FULL S C A L E
A L L UP W E I G H T = 2.,50,f3K)O L B .
. ,
ALL UP WEIGHT=340,O00
LB.
21. Effect of all-rip weight on stability and trim of fi~]al form,
~od. AK: Take-off. Flaps 15 deg. C.G. normal, 30.g per cent S.M.C.
FIG.
FIG. 22. Effect of all-up weight on stability and trim of final form,
Hod. AK. Landing. Flaps 45 deg. C.G. normal, 28.2 per cent S.M.C.
G~EEN WATER
UGH]" SP~AY
P~)PELLER SPRAY INTERFERENCE
III
\\\
TAILPLANE
////I~/IN~
,SPR/k¥ IN'W.RFERENCE
~ N
WA'TF=~
LIE+IT 8,PRAY
SPRAY INTERFERENCE
14
III
S
, \ \ \\
•
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\
r~
//
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,
,
\"
I~IOPE.LLER SP'I~.Y INT'F..RFERENC..E
//,/
~
-
WING SPRAy INTERFERENCE
TAILPLANE ,SPRA~"INTERFE~NCE
/ /
\\\
" /
14
xx\'~
J
2
,
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, x " ~ ."..,.,'X. ~
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I
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F-
K.AP.S 0"
40
50
,GO
70
,~O
SPEED- KNOTS FLLL ,.SCALE.
90
IOO
IIO
~
~
,t.-~o"
\
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130
~ "¢/-~
120
,,k
/,,
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1513
X
I
FLAPS O°
I
bO
~O
ZO
543
4O
50
70
80
80
SPEED- KNOTS FULl. SCALE
IO0
I[O
I~0
130
14
IZ
\
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/J
\\\
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\ .<\x
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w
ot
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22~...~.'c"
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23
j
x
}44\i x\\% \ \ \" \
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2-0
30
40
E,O
60
70
~O
SPEED- KNOTS FULL .SCALE
SO
}OO
IIO
120
I30
FIG. 23. Effect of flaps on spray interference on final form, Mod. AK.
Take-off at 310,000 lb. C.G. normal, 30.2 per cent S.M.C.
oi
fO
~O
t13
40
50
El
70
80
.SEED- ]<bIOT,S FULL .SCALE
~O
IOO
I10
I;:'O
150
FIG. 24. Effect of flaps on spray interference on final form, Mod. AK.
Take-off at 340,000 lb. C.G. normal, 30.2 per cent S.M.C.
~BO,OOQ
ALL UP
WEIGHT (LB)
~60,000
GREEN WATER
340,000
LIGHT
300, 000
8O
ZO
4-0
GO
SPEED- KNOTS FULL SCALE
0
SPRAY
PROPELLER INTERFERENCE FLAPS
O ° & IS?
58[
I
NOT TESTED AT
HIGHER WEIGHTS
All
WE
/
,/
0
ZO
40
5PF.F.D-KNOTS
GO
FULLSCALE
8O
0
2.o
4-O
C~O
SPEED- !KNOTS FULL SCALE
FLAPS 15°
FLAPS
°°kb
) Ix
WING
80
INTERFERENCE.
U
NOTTESTED
WEIGHlt
AT HIGHER
WEIGHTS
,
0
?O
4O
GO
SPEED " KNOTS FULL SCALE
FLAPS O *
C)
300,000
SO
O
-Ix~
ZO
4O
GO
SPEED- KNOTS FULLSCALE
&O
FLAPS 15°
TAILPLANE
INTERFERENCE,
FIGS. 25a, 25b and 25c. Effect of all-up weight on spray interference on final form, Mod. AK.
Take-off. C.G. normal, 30.2 per cent S.M.C. *l = --6 deg.
30
~r = 3 . 0 ° ; 1 2 . 5 k n o t s
~'~r = 7 . 3 °', 3 1 . 3 k n o t s
FIG. 26.
~x ---- 5 "0° ; 1 8 . 8 k n o t s
~qr = 10 .00 ; 37"6 k n o t s
P r o p e l l e r s p r a y interference o n final form, Mod. A K . Take-off a t 310,000 lb.
C.G. n o r m a l , 3 0 - 2 per c e n t S.M.C.
~s = 5 " 9 ° ; 2 5 . 1 k n o t s
~Jr = 10"2° ; 4 3 . 8 k n o t s
F l a p s 0 deg.
g
~
---- 3 . 0 ° ; 1 2 " 5 k n o t s
~r = 5.1 ° ; 18.8 knots
~x = 5 . 9 °', 2 5 . 1 k n o t s
~E =
",r - " 10"7 ° ;
¢,O
tO
• x ---- 7 " 8 ° ; 3 1 " 3 k n o t s
!
u
FIG. 27.
10"3° ;
37.6 knots
P r o p e l l e r s p r a y i n t e r f e r e n c e o n f i n a l f o r m , M o d . A K . T a k e - o f f a t 340,000 lb.
C.G. n o r m a l , 3 0 . 2 p e r c e n t S.M.C.
F l a p s 0 deg.
43.8 knots
No &
No o 283"
.t
"7"
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