The tailless configuration for
carrier ops iss2 Prof. Prodyut Das
“I seriously want to know your
aeronautical opinion of the F7U Cutlass or F4D Skyray. Cutlass had all sorts of
mods to make it work on a carrier but the crash rate was its defining descriptor.
Skyray was loved by pilots but it was quickly superceded by F8U and F4H
aircraft.”
Dear Mike Mueller. It is always a
pleasure to exchange views on aircraft though the two you chose are somewhat of
rara avi! Since you have a background of having worked in a Grey Funnel
Line you may find some of the explanatory notes “known” stuff
but I am an Indian and write for a largely Indian audience; there are
those who like a more informative “Aufklarung” style with “patter”. With
that as an introduction let us begin:
The fall of Nazi Germany was the
aeronautical equivalent of the fall of Constantinople- it started an
aeronautical renaissance in the US. The amount of high-quality data,
prototypes and ideas that the 3rd Reich had generated in the
last three years of its existence was both incredible and exciting. Together
with the data came, quite often, their now out of work originators- Von Braun,
Oberth, Lippisch, Brandner (he went to the CCCP) ,Hoerner their catalysis (I
use the word advisedly) was such that almost overnight the US and USSR
graduated from Great Powers to Superpower status. I do not exaggerate; Project Manhattan gave
the US the Atom Bomb but without the German Technology providing the rocket
engines it would be of no earthly use, the MiG 15 making the B 29 obsolete by
1950s.
The impact of that advanced German
thinking was possibly mind blowing to the Americans. If you think I am
belittling just compare the solidly engineered but antediluvian Bell
Airacomet or Douglas Pirate or even the prototype XP 86 Sabre (with its
straight wing) with the Hortens, and Messerschmitt 262,163 or P1121 and one can
imagine the exciting vision the Germans presented. The root of the difference
lay in the way Designers thought. The Allied Designer’s viewed the Jet engine
as just another more powerful means of propulsion -Meteor, Su-17 (the first
one) or even the Lockheed P80 whereas the Germans with their Technisches
Mechanik approach integrated the new propulsion conceptually from the
ground up. It is like something one often sees in the design of advanced
plastics replacing metal parts. Some exploit the characteristics of the plastic
to make a much better design with fewer sub-assemblies and other “designers”
simply reproduce the metal part in polycarbonate. Similarly with electric
flight.
I suspect there may also have been a fair
amount of “Technology Gawking”. If one sees a masterly use of new technology
some people become convinced that it is a “sure to win” formulae. It is quite
possible that, however briefly, the US designers were hustled into “gawking” -sort
of thinking “if the Germans/Nazis have done it and they were a whisker
away from success then with a bit more of effort and Yankee ingenuity it would
surely the winning formula. The various Bell X planes, the doodle bugs ,
Redstones were witness to that line of thinking. Dr. Alexander Lippisch, the
master of the “Tailless with fin” layout was present in the US and he is said
to have influenced the Convair F 102 / F106 tailless Deltas which in turn
stemmed from the tailless technology Demonstrator Convair XF 92 with its pure
plain delta wing.
Nothing wrong with the plain delta-If
your game is high altitude, i.e. > 12,000 mts, supersonic bomber intercept
the pure Delta is a very acceptable choice. It offers a large surface area for
high altitude performance; the big root chord means a great root spar depth and
thus a light structure without requiring milled skins and the internal volume
is wonderful for storing fuel. It negative points are that the “tail volume” is
low and since the elevons go “down” to generate lift sustained turn rate is
poor as is airfield performance. So why did Heinmann, one of the legends of
Aircraft design choose the plain delta?
The possible “drivers” were:
1.
The specifications, in a
manner of speaking, called for a manned SAM with a terrific- for the time-
climb rate. The Delta was perfect in this niche offering low drag, large area good fuel volume.-
2.
The carrier lift size
limited the wing span so again the delta scored by packing the maximum area
within the smallest span.
3.
By this time Heinmann had
been hooked to the “non- folding” wing. He argued that not folding the wing
saved him 28 lbs. per joint and the delta gave him the area within the span
which would fit into the lift and not need two heavy “joints”. teh cutaway does not show if the F4D had wing folding, Do you know? The A4D "Scooter" did not have nay I know.
4.
The “poor” field performance
of the delta- poor lift at low airspeeds did not matter quite so much given
CATOBAR operations.
5.
The poor view over the nose
during approaches was cured by putting the cockpit almost right in front and
carefully area ruled including a bulge canopy so that aerodynamic “bluntness”
was avoided.
The tailless delta is a niche
configuration and Heinmann, an old stager in Shipboard aircraft had found that very restricted niche for a rather primitive, limited
specification. Why have I put very restricted in italics. The
Douglas F4D was going to operate from the Forrestal class CVs. Given the
parameters I doubt they could operate from the Indian CVs past or present. As
you have also noted, Heinmann, the popularity of the “Ford” notwithstanding,
went for the tailed Delta in his post war magnum opus the A4D Skyhawk.
Now why would a “great” do that unless he realized the advantages?
The tailless Vought Cutlass had as
legendary a pedigree as the Douglas F4D (“Ford in USN service) Skyray . Vought was the maker of the
“Sweetheart of Okinawa” the F4 Corsair and its designer Rex Beisel was the very
same man but as mentioned earlier that many Aircraft designers, as with
designers in plastics, were probably unable to think “jets”- the great Soviet
designer Seymoun Lavochkin being one such who was unable to make the
transition.
Why was the F4D Skyray “successful” and
the other Vought Cutlass was not? Sometimes a simple table can be quite
telling.
Table 1
|
Sl.No |
Type |
Fuselage
length |
Wing
Loading |
Span
Loading |
Thrust/wt |
We/Wmto |
Aspect
Ratio |
|
1 |
Vought
Cutlass |
12.1 |
311 |
1187 |
3.81N/kg |
0.573 |
3.11 |
|
2 |
Douglas
F4D Skyray |
13.93 |
221 |
1110 |
5.7N/kg |
0.641 |
2.1 |
|
3 |
Tejas
NLCA |
13.2 |
330 |
1609 |
6.36 |
0.67 |
1.68 |
People tended to blame the high accident
rates of the Cutlass on its novel tailless configuration but that was probably not the case.
The accident rate was some 90 accidents in 55000 flight hours in ten years of
colour service using about 200 airframes, 50 airframes being written off. The
flight hours indicates unreliable systems which precluded greater utilization.
The several spectacular ramp strikes can be traced to the high wing loading and the low
power loadings of the Cutlass. Once the pilot realized he was in a ramp strike
situation he had little means to wriggle out given the poor T/W and the high Wing loading. Otherwise, it was not as bad an aircraft
as it is made out to be had its engines been more reliable- something like the
EE Lightning engine fires which came apparently stacking teh engines one on top of the other but of course teh Lightning was quite another thing in terms of handling.,
The figures explain the why the Ford was
loved. Good balance of parameters. Why did they go out after relatively short service?. Look at the fuselage
length. There was no scope for future growth. If you can easily get a copy of Air
International (a British Magazine) Vol 23 No 4 October 1982 there is an article
by the great Man Ed Heinmann himself along with a good cutaway and some of his
views on a future fighter, He proposes a canard (with the intakes correctly
positioned) with all the tricks he used to keep the A4D “Scooter”s weight down.
If you can get it easily you, might want to read it. He also talks about
the Skylancer F5D and his disappointment the F8U won over his F5D. I am not saying it is a must read but if you can....
Since I know Local readers would be curious about the NLCA I have for convenience included the ADA Tejas figures but refrain from commenting because the Carrier size, Wind over deck, and CATOBAR vs the ski jump respectively of the USN and IN figures are beyond my ken. What the figures tell me is that even giving the FBW and the MUCH higher T/W the very low AR means acute alpha sensitivity on the part of the pilot and ...well I leave it at that. The Navy will know.
Why were the two types superseded very
rapidly. The 200 Cutlasses barely lasted 10 years mainly due to poor systems
design rather than aerodynamic tricks that is generally supposed to be inherent to
the tailless layout and the 479 Fords went out by mid 6os because the small
fuselage volume. look at a cutaway. The systems sure took up a lot of space. The USN does not waste time trying to make a go of something that inherently
has limited potential and both F4D and teh Cutlass had no volume..
My concluding remarks would be that the tailless
layout per se has very few problems, specially the Lippisch type with a
central fin. The Me 163 by all accounts had good flying characteristics but
often as it happens, other problems- the stiff skid landing gear and the
hypergolic fuels gave the aircraft a sclechten rufe! The British
troubles with the DH Swallow was one of self- created problems. I do not think
today one would even allow a wooden fuselage aircraft with 12 percent
thick wing to make supersonic dives. The severe vibrations apparently broke the
pilot’s neck. The other British Flying wing the AW52 was looks wise leery. If
you stick large end plate fins at the tips of a slender wing, well structurally, even
without calculations, you know you are asking for all sorts of aeroelastic and
control problems.
The ideal usage of the tailless is
probably in the subsonic electric flight. I think in this blog somewhere
in 2021 I posted about the Zanonia a design by Prasenjit Das and myself on an
electric Utility aircraft. It took a place in the R.Ae.S of UK competition in
2021. You might read that.
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