Elliot Dent flew with the 7th Fighter Squadron of the 49th Fighter Group. He was credited with 6 Japanese fighters destroyed in combat, flying both the P-40N and later, the P-38L-1-LO.
Before his death, Dent wrote a little piece about the P-38, which was later published by his son-in-law. I posted this to this board over 3 years ago. Perhaps it is time to post it again.
Understand this though, Dent flew the P-40 and P-38 in combat. He also flew the P-47 and P-51 stateside. His fighter of choice was the Lightning and he tells us why.
"Other than knowing how to handle an engine-out situation on take-off (the usual
VMC business), the Lockheed offered no trouble. A complex airplane? For its
day, yes. A dangerous airplane? Not at all.
This P-38 debate is endless, but some things about the P-38 that made it such
a marvelous design haven't been brought up that probably should be:
To achieve high-speed capability, an airplane will have high wing-loading
(gross weight to wing area) and low power loading (gross weight to horsepower).
The P-38 had very high wing loading (which provides other benefits, such as
when penetrating weather, etc.), higher than anything other than one-off
record-breaking and racing planes when it was introduced. And it also had
unusually low power loading; in fact it had the lowest power loading of any US
design (maybe any design) of WWII. Turbocharging ensured this power loading
would remain constant to very high altitudes.This meant the airplane would be fast.
But high wing loading would normally degrade turning, climb and ceiling. With such
high wing-loading, the P-38 should have been a dog in all but top speed. It wasn't
because of two other factors.
One is its aspect ratio (span to chord ratio; that is, the relationship of the
length of the wing to its width). Another, related, factor is its span loading
(ratio of airplane weight to wingspan). In turns or climbs, a plane's drag tends
to increase and its speed to decrease. A way to counter this is to increase
the wingspan. For any given wing area, increasing the span decreases the
chord, providing a higher aspect ratio. For structural and other reasons, most
WWII-era fighters had aspect ratios of 6 or less. The P-38 had an amazing
aspect ratio of 8, meaning that it could gain the advantage of high wing loading
for speed and still not lose in maneuverability, climb or ceiling.
A large wingspan, however, generally degrades a plane's rate of roll because
the wing surface is so far out from the fuselage and center of gravity. Making
the wing tips narrower by tapering the plan form does a lot to counter this.
Normal fighter configurations had a taper ratio of about 2 (the wing tip being
only about half as wide as the wing root). The P-38 had a taper ratio of 3.
So, you had an airplane that was fast yet a good climber, a good turner and
good roller.
But wait--there's more:
Power has to be converted to thrust thru a propeller. Big powerful engines
need big propellers to handle that power, but the diameter of a prop is limited
by tip speed. So power has to be absorbed by adding blades or increasing their
width. But a prop working harder on a given volume of air has inherent
aerodynamic inefficiencies requiring performance compromises. Bottom line
being that propeller inefficiency limits the value of engine power.
But because the P-38's power was in two "sections" (engines), each with its own
propeller, it was able to use its power as efficiently as a much lower-powered
airplane operating at lower speeds. And the increased propeller disc area of
the two props ensured that the plane's power and thrust would be maximized
throughout the maneuver range. This thrust efficiency made for an airplane that
leaped into the sky on take-off and could accelerate in the air like a drag racer.
Pretty neat, huh?
But wait--there's more:
Ordinary fighters of the day had a tail length ratio (number of times the wing
chord goes into the distance from the center of gravity to the tail surfaces)
of between 2 and 2.5. This ratio might be compared to wheelbase on a car. A
shorter wheelbase makes for a choppier, less stable ride. The P-38's tail
length ratio was a whopping 4. This means it had excellent damping, or the
tendency to slow the rate of departure from a trimmed position. This made it a
great plane for flying long distances in, with one finger on the wheel, or for
instrument flying, or as a steady gun platform or for dropping bombs.
The large tail length ratio required a smaller than normal tail surface area
because of the increased arm at which the surface worked. This reduced drag
and made for a truly excellent flying airplane.
Not bad, huh?
But wait--there's more:
The width of the horizontal tail surface was determined by the spacing of the
booms. The result was a very high aspect ratio for the tail plane. The
endplate effect of the two vertical fins and rudder surfaces on the end of the
booms produced an aerodynamic apparent aspect ratio that was even higher.
This had the effect of providing very rapid changes in force with small changes in
the aircraft's angle of attack. This great sensitivity, combined with superb
damping, meant that less trimming force was necessary for stability and that
there was a wide range of CG position or stability available without
degradation of flying characteristics.
Wow, man!
But wait--there's more:
The high aspect ratio of the horizontal tail also produced narrow chord
elevators, which in a turn meant light control forces for maneuver. Ditto for
the vertical tail surfaces and rudders. Net effect, the pilot could dance the
airplane all over the sky without breaking a sweat, while bellowing out the
latest tunes from "Oklahoma!" to drown out the curses in his headphones of any
other pilot in some lesser machine that he chose to sky-wrassle with.
Because the engines rotated in opposite directions, they produced a symmetrical
slip stream flow which eliminated the need the carry rudder displacement, thus
reducing a source of drag. And there was no change in trim with changes in
speed, which was a pure blessing in maneuver combat, er, dogfight.
Then there is the Fowler flap system which actually increases wing area,
tricycle landing gear, centerline fire guns, plenty of internal fuel, a roomy
cockpit....
The P-38 also had an amazing degree of detail refinement compared to other
planes. All its external surfaces were smooth with no disturbances from rivets
or lap joints, for example.
One negative was necessarily small ailerons because of the wing taper, meaning
large aileron displacement would be necessary to initiate a roll. That meant
high aileron forces. That's why the control wheel was used, and why the later
models had aileron boost. Savvy pilots would blip the inside throttle when
they wanted a smart roll ASAP. Less savvy pilots did lots of pushups. And
there was the cockpit heating and defrosting thing (by the way, it's just as
cold at 25,000 ft. in the tropics as in Europe), which did get solved about as
soon as it became apparent. Cooling was never as effectively solved.
But, all in all, a pretty damned good flying machine.
As pilots of the day said, if Jesus came back as an airplane, he would be a
P-38."
Elliot Dent
