--Went to the Mathers AFB air show this past weekend and got to see
4 of the 7 remaining P-38 Lightnings flying. I know they had Allison engines
and I remember the P-51s originally had these as well. Well the P-51 got the
Merlin and a huge boost in performance; why didn't this happen to the P-38s
as well? Talking to a pal at the show we decided it was due to a production
bottleneck; i.e. they couldn't be made in sufficient quantities to equip the
twin engine aircraft. Anyone know the truth of the matter?
> =A0 =A0 =A0 =A0 --Went to the Mathers AFB air show this past weekend and = got to see
> 4 of the 7 remaining P-38 Lightnings flying. I know they had Allison engi= nes
> and I remember the P-51s originally had these as well. Well the P-51 got = the
> Merlin and a huge boost in performance; why didn't this happen to the P-3= 8s
> as well? Talking to a pal at the show we decided it was due to a producti= on
> bottleneck; i.e. they couldn't be made in sufficient quantities to equip = the
> twin engine aircraft. Anyone know the truth of the matter?
>
> --
> =A0 =A0 =A0 =A0 "Steamboat Ed" Haas =A0 =A0 =A0 =A0 : =A0Beauty times bra= ins =A0
> =A0 =A0 =A0 =A0 Hacking the Trailing Edge! =A0: =A0is a constant..
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0www.nmpproducts.com
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0---Decks a-wash in a sea of words-=
The P-38 didn't need a moderate increase in power..
By virtue of having two engines it had twice the power of the P-51.
The very early ones had engines that turned the same direction.
The torque and P-factor made for a hand full under even fairly normal
takeoff conditions. They were quickly replaced with engines that turned
opposite directions which tamed the beast. Which is probably the real
answer to your question.
Its an awesome airplane!
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Flight Characteristics of the P-38
(video 35 minutes)
They had counter-rotating props since day 1. The prototype had them
arranged for best engine-out performance, but that set up some weird
turbulence on the center section and tail, so they were reversed.
From the one book I had on the P-38 it was politics: the RR was a
better engine at high altitude, but GM didn't want to see any more work
going to Rolls.
But it was probably a bunch of reasons -- things are never simple.
> =A0 =A0 =A0 =A0 --Went to the Mathers AFB air show this past weekend and = got to see
> 4 of the 7 remaining P-38 Lightnings flying. I know they had Allison engi= nes
> and I remember the P-51s originally had these as well. Well the P-51 got = the
> Merlin and a huge boost in performance; why didn't this happen to the P-3= 8s
> as well? Talking to a pal at the show we decided it was due to a producti= on
> bottleneck; i.e. they couldn't be made in sufficient quantities to equip = the
> twin engine aircraft. Anyone know the truth of the matter?
>
> --
> =A0 =A0 =A0 =A0 "Steamboat Ed" Haas =A0 =A0 =A0 =A0 : =A0Beauty times bra= ins =A0
> =A0 =A0 =A0 =A0 Hacking the Trailing Edge! =A0: =A0is a constant..
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0www.nmpproducts.com
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0---Decks a-wash in a sea of words-=
Actually, the Merlin used in the P-51 was reversed from the Rolls, and
built by Packard under license.
The P-38 didn't need a performance boost primarily because it was
turbocharged. The P-39 was hamstrung by its Allison because the Army,
in its infinite wisdom had the two speed supercharger replaced with a
single speed supercharger, which really limited performance at
altitude. The P-38 didn't have that problem.
The P-38 is one of the few army fighters Dad didn't fly during the war
(he flew the P-39, 40, 47, and 51). That was the one he really wanted
to get in, and would've if he hadn't transferred from the Pacific at
the end of '43. But after a year and a half out there, who wouldn't
have jumped on a chance to go home for a while. He got in the 47's
and 51's in Europe after that.
Pete Keillor
I think the issue was the turbosuperchargers. The American design
needed a lot of room for the intercoolers etc so it was used in larger
aircraft like bombers and the P-47. In a small fighter the space right
behind the engine was close to the center of gravity and too valuable
for fuel to waste on turbo air pipes.
It was reputedly too troublesome when installed in a rear-engined
small aircraft like the P-39. The P-38 initially used the leading edge
of the wing for the intercooler but that proved to be unreliable.
The British two stage supercharger was more compact. The Allison did
have an integral one-stage supercharger attached to the crankcase.
Sir StanleyHooker
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Sanford Moss
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I don't have this yet:
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I haven't found much technically-oriented detail on this matter on the
Net, or on WW2 aircraft construction in general. I do have graphs that
show the relative performances of several of the schemes tested, and
mention of the severe weight and reliability problems of variable-
speed drives like clutches or the Hydramatic transmission.
The problem is that a supercharger absorbs several hundred horsepower
and unless disconnected it denies the aircraft that power even at low
altitudes including takeoff. They size it to give full engine power at
the altitude of predicted combat, assuming the enemy follows the plan.
Below that altitude it can boost the manifold pressure excessively and
damage the engine. Ideally you would drive it with an automatic
continuously variable ratio transmission, if one were available then
(or now).
The turbosupercharger with waste gate was a partial answer in a
fuselage or nacelle large enough for the plumbing. GE simply couldn't
make enough of them fast enough.
The P-38 and P-39 were both designed to the same request for an
interceptor. The 38 was more promising so the 39 was repurposed for
ground attack, partly to keep Bell from closing. At low altitude the
P-39 was good enough to tangle with a Zero with some chance of
success. If you look at the power vs altitude chart referenced in my
other post you'll see that the low-altitude engine has more power
close to the ground, down where all the strafing and bombing targets
are.
The P-40 was also intended for low level ground support use since in
the late 30's no heavy bomber could threaten the continental US, only
smaller carrier aircraft could get close enough. We were far too
isolationist to spend scarce funds to prepare for major overseas land
operations. Those who knew better counted on several years of
preparation time between the start of a war and serious attacks on the
US. That's why we had battleships and carriers but too few antisub
escorts, which are quicker to build when needed.
Today the F-22 andF-35 suffer the same opposition. It seems we need an
occasional Pearl Harbor or 9/11 to silence the delusion that the world
will be safe if we all think peaceful thoughts. We'll have peace only
when everyone believes they have justice.
jsw
I've had the joy of seeing P-38's fly at Oskosh EAA. My feeble brain, when
seeing the
subject line for this thread, was going oh goodie, plane, pistol or can opener.
All
devices I admire.
Almost bought a P-38 once but I did enough research to realise it was an
afterwar alloy
frame model. (pistol) Damn. There are three iconic guns I don't have yet, the
Lugar,
P-38, and the M1911.
Some machines exude sex and hormones. Think Italian sports cars and the P-38
Lightning,
like Raquel in her advanced age, is still hot!
Wes
e P-38 Lightning,
My father who was an Air Corps ordnance company CO in the Pacific said
the pilots didn't really like the P-38. He didn't know why, but the
plane was very advanced for its time and had a lot of teething
problems, some very serious like loss of control in a high speed dive.
Sometimes the thicker air down low slowed it enough to regain control,
sometimes it didn't.....
The closest I'll ever get to flying one is a sim, where it's not
nearly the most nimble WW2 fighter and can flip out suddenly if turned
too hard too slow. #2 US ace Tommy McGuire crashed that way while
chasing a Zero at low level.
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As far as I can tell the MS sims are reasonably accurate. If so, I'll
take a land-based Corsair, please.
The sim Lightning does have a lot of 20mm firepower and unlike some
others is stable enough to tear up small ground targets from several
thousand feet. In Combat Flight Sim 2 it can set fire to and
eventually sink a warship. Shooting up the whole Japanese Navy in
volcano-rimmed Rabaul harbor on an HDTV monitor is a lot of fun.
jsw
Yup, and they'll kill your ass. Jeff Ethell, the photographer, bought
it at Tillamook in the classic P-38 crash, engine out followed by spin
in. And his dad, a P-38 vet with 10,000 hrs witnessed the crash. The
manual says if you're below a fairly high speed, I think 120 with
flaps or thereabouts, and you lose an engine, you immediately chop the
other engine and go in straight ahead. Below some speed, and Ethell
was observed to be going "too slow", you can't keep that thing from
spinning on one engine.
Pete Keillor
Lightning,
Can't help but contrasting that with the Israeli F-15 jockey who brought
it home on one wing. A lot of improvement in technology there that is
not noticeable until something goes badly wrong.
As a general statement two speed superchargers were designed to give
max rated boost in low speed for takeoff, i.e. ~ sea level, while the
high speed was used at altitude. At least that is how the radial
engines were designed. After the advent of turbos, I don't believe
that two speed superchargers were used to any extent. At least the
C-97, which as far as I know, was the last strategic reciprocating
engine airplane used by the A.F. had a single speed supercharger and
turbos.
The procedure for shifting to high blower, by the way, involved
throttling back a bit, to prevent over boosting, shift to high speed,
and then reset throttles for desired manifold pressure.
Cheers,
John D. Slocomb
(jdslocombatgmail)
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