P-38 vs P-51

[DerAdlerIstGelandet]

But he clearly felt chastised all the same.

Well I sent him a PM. He can return if he chooses.

 

[BiffF15]

Regarding the P-38

Advantages

1. Performance
   • The earlier P-38's (E/F) had a superior rate of climb to the unlettered P-51's; against the P-51A it was superior from 0-5000 and from around 20,000 feet up
   • The earlier P-38's (F/G) seemed to be able to out accelerate earlier P-51 models (P-51/P-51A) in level flight from 0-250 mph and probably a bit above that
   • I would not be surprised if it would out-accelerate the P-51 in a dive initially due to it's greater mass -- I wouldn't do it long though (mach tuck is a bitch).
   • The P-38's seemed to have better zoom climb performance all the way up to the P-51B at least, while close -- it'd hang on a bit longer.
   • The P-38J's long-range wing-tanks didn't upset the CG as much as the Mustang's did, so it didn't require as much burning of internal fuel before switching to drop-tanks.
2. Armament
   • The armament centered in the nose provides a greater range of, well, ranges where it can accurately hit other aircraft
   • The 20mm cannon also provides substantial hitting power over the P-51's all 0.50 armament
   • It was able to carry substantial bomb-loads, around 3200 lbs if I recall versus the Merlin powered P-51's 2000 lb loads
3. Other
   • The nose-gear made for easier landings, better initial acceleration on takeoff, and better visibility when taxiing
   • Rear visibility was probably better on the P-38 up to the P-51D owing to the shape of it's canopy
   • It might have had more docile stall-characteristics, and might have been easier to land on short-fields
   • The extra engine might have made for greater survivability when flying over oceans and possibly even in air-to-ground configurations (that said, the P-47 is king in air-to-ground).

Disadvantages

1. Performance
   • The P-51 had a faster rate of roll than the P-38's until the P-38J/N came around
   • The P-51 had a much faster critical mach number and placard limits in dives than any aircraft in the USAAF inventory, as far as I know.
   • The P-51A had a superior rate of climb from about 5000-15000 feet, which is a very useful altitude block
   • The P-51B had a superior rate of climb from below 10,000 - 15,000 feet or so, and above 25,000 feet.
2. Armament: I'm not sure if the P-51 had any advantage except that it had more guns
3. Other
   • The cockpit was said to be better designed from a human-factors standpoint than the P-38
   • The cockpit seemed to have less issues with extreme cold and frosting in the cockpit over the P-38
   • The P-51D's cockpit probably had better visibility, overall, to the rear hemisphere

I could be wrong on this, but that's basically what I seem to have grasped so far. I am curious how fast the P-38 could go with the dive recovery flaps in terms of mach number.


That's an interesting piece of data that I didn't know prior to this point

While off topic: What kind of rate of climb are we talking about?

Very valuable data

That looks more like a bowling ball than a baby...

Any more mass quoting and Fubar57's going to be apoplectic

Zipper,

Having sat in a P38 and a Mustang, it is my opine that all versions of the P51 have better visibility. The P38 might have a touch better at 6, but everywhere else it lagged. Don't get me wrong, the 38 is an awesome plane, however the two engines, in your 10 & 2 o'clock along with the booms and all the girders in the canopy were less than optimum.

Also the boosted ailerons might allow a higher roll rate eventually, I would doubt it would be greater through the first 180 degrees due to the mass that would need to be moved.

Cheers,
Biff

 

[XBe02Drvr]

Also the boosted ailerons might allow a higher roll rate eventually, I would doubt it would be greater through the first 180 degrees due to the mass that would need to be moved.

Also I remember reading the boosted ailerons had no "proportional" response capability; they were "all or nothing" like an old escapement type radio control model.
Cheers,
Wes

 

[swampyankee]

Overall, the P-38 was an effective combat aircraft, especially after some basic defects were worked out, that is the engine installation issues, cockpit heating, poor roll rate, and the pilot training was upgraded so that engine out conditions didn't end up with crashes. Obviously, the high Mach number problems weren't really fixed -- the compressibility flaps were a crutch -- but those were less problematic outside of USAAF bomber escort over Germany. What wasn't fixable was that the P-38 was much more expensive to produce (twice the propellers, twice the engines) and maintain than the P-51.

 

[CORSNING]

I was actually shooting for an earlier version without the water injection and 8 guns.

Don't bother, not enough difference to worry about. The earlier version was slower by 6mph at 27000' and 300fpm at 20000'. Enjoy the time with your family. [/QUOTE]

Thank you sir, I did enjoy the time with my family.
Now it is time to dig deeper into research and calculations. I am currently studying
many subjects all at once. The P-47D-6 and P-47C are in that category. I am currently
searching my files and wwiiaircraftperformance.org for the answers. HOWEVER, when
I post the new information, I believe it belongs on the P-39 vs. P-47...er uh vs. P-40
thread. That is where I shall post it when time permits.

I am also working up a P-39N / P-40N-1 / P-51A comparison of Allison single engine
fighters of 1943.....very interesting by the way. That baby will have to go on the
P-39 vs. P-47...er uh vs. P-40 thread also.

This all sounds like fun to me....I have to work the next 5 days in a row, so it may take
some time......................................DAMMIT!

 

[Zipper730]

Having sat in a P38 and a Mustang, it is my opine that all versions of the P51 have better visibility. The P38 might have a touch better at 6, but everywhere else it lagged.

I rewrote the earlier bit and corrected that the visibility was superior from the front and sides on the P-51 through P-51C, and superior to the rear as well on the P-51D. Regarding the P-38, I put visibility was superior to the rear prior to the P-51D

 

[Zipper730]

As far as I know, the P38 (and perhaps the Mosquito) was unique in this regard due to its extremely high power to weight ratio and the rotation direction of its counter-rotating propellers giving both engines "critical" behavior regardless of which one fails.

I thought a critical engine was the one to most affect yaw? From the descriptions of the P-38 it seems that each engine would basically cause a loss of control if either kept at full power or pushed to emergency power

 

[FLYBOYJ]

I thought a critical engine was the one to most affect yaw? From the descriptions of the P-38 it seems that each engine would basically cause a loss of control if either kept at full power or pushed to emergency power

When a P-38 lost an engine, the yaw affect was the same (therefore no critical engine or both engines were"critical engines" depending on who's semantics you want to play with) and for the most part the emergency procedures were the same on either engine. As previously mentioned, if you lost an engine at higher power settings (like during take off) you have to reduce power on the good engine first then go into emergency procedures for the failed engine. Loss of control was the main concern during take off as airspeed and altitude was limited and the landing gear would more than likely be down.

 

[Ivan1GFP]

I thought a critical engine was the one to most affect yaw? From the descriptions of the P-38 it seems that each engine would basically cause a loss of control if either kept at full power or pushed to emergency power

Hello Zipper730,
With twin engine aircraft, usually the propellers both rotate in the same direction.
In that case, losing power to the inboard rotating propeller leaves the outboard rotating propeller turning which has a greater effect on the lateral and directional control of the aircraft.
The reason is that the torque effect of the inboard rotating propeller tends to compensate a bit for the lateral offset of the thrust while the outboard rotating propeller torque tends to add to the effect of the lateral offset of the thrust.
Thus loss of the inboard rotating propeller causes the most adverse control effects which makes it the critical engine.
In the case of the P-38, both propellers rotated outboard, so loss of either engine would cause equally bad control effects. From an expectation of effects, I would consider both engines to be critical, but neither has a greater effect, so one could also call NEITHER engine critical.

- Ivan.

 

[FLYBOYJ]

Another consideration for determining critical engine would be the accessories carried within the engine or QEC. As mentioned, early P-38s had one generator on the left engine, I believe there was one hydraulic pump as well, so this would put the left engine as the critical engine. I believe the P-38J doubled up all engine driven accessories.

 

[Marcel]

This is a forum where the mods are more abusive than the participants and worse in their ignorance and partisan views.

Thanks, I guess? Did not know I was abusive and had partisan views. Ignorant might be, one cannot know everything I guess.

 

[XBe02Drvr]

Thanks, I guess? Did not know I was abusive and had partisan views. Ignorant might be, one cannot know everything I guess.

PAR TI SAN (noun): One who views his own views as fact and differing views as partisan.

To quote the Firesign Theater, I think "We're All Bozos on this Bus".
By being here, we all choose to live with it.
That's what makes it great.
And a happy new year to all!
Cheers,
Wes

 

[XBe02Drvr]

it seems that each engine would basically cause a loss of control if either kept at full power or pushed to emergency power

ONLY IF you're below VMCa, as in takeoff, slow flight, or on a go-around.
IIRC, VMCa at full power was somewhere around 150 mph, on an airframe that was usually ready to fly at about 100, leaving you with a 50 mph "danger zone".
If you're carrying max range fuel and ordnance for a strike at Rabaul from Guadalcanal, and you lose your left engine (with your only generator and only hydraulic pump) right after liftoff, you have a CRITICAL SITUATION.
If you don't INSTANTLY reduce power on your right engine, you're going to flip inverted and go in on your back. If you do manage to get the power reduced and apply 100+ pounds pressure to the right rudder pedal, you've got a heavy, draggy, dirty, airplane (gear down, one notch flaps down, racks full of fuel tanks and ordnance, and no hydraulic or electrical power, except maybe ten minutes battery), that you're trying to fly on one off-center engine at reduced power. Say your prayers, stay in ground effect, and get over water ASAP, so you can ditch your payload.
If you're still alive by then, relax a little and see if you can coax her up over VMCa and get a little more power on and relax the cramps in your right leg a little.
Congratulations, you made it! Now you can get a little rack time and be rested for tomorrow's strike mission.
Cheers,
Wes

 

[Zipper730]

IF you're below VMCa, as in takeoff, slow flight, or on a go-around. IIRC, VMCa at full power was somewhere around 150 mph, on an airframe that was usually ready to fly at about 100, leaving you with a 50 mph "danger zone".

Means an inch away from ending up as barbacoa...

 

[Graeme]

A couple of "Good Points" on having two engines as listed by Col Oliver B. Taylor, Commander of the the 14th Fighter Group in 1944...

(From P-38 Lightning - Ethell - Jane's, 1983 - pp 23)

 

[XBe02Drvr]

Means an inch away from ending up as barbacoa...

Maybe a couple of inches (manifold pressure) away!
Put yourself in the pilot's seat.
Your heavily laden bird has probably stayed in ground lover mode a little longer than usual, so you may already be 10-15 mph into the danger zone before you get airborne. If your left engine quits now, suddenly and totally, your plane instantly starts to swing, and then bank, left. You need to INSTANTLY retard both throttles and STAND on the right rudder with all your might, while shoving forward on the yoke to hang onto the speed you already have. This takes guts, as it's going to feel like you're falling out of the sky, and you will if you don't get a little power back on soon.
Now, if you're fortunate enough to have stopped the turn and you're still flying, you need to find out how much power you can give the right engine without overpowering that rudder and your already shaking right leg. If you have enough control authority to get into a 3°-5° bank to the right, it will improve your performance slightly and give you a better chance of survival. Remember, this all started right after liftoff, and you haven't gained any altitude, so you're probably dodging obstacles to boot, and ground effect is the only thing keeping you alive.
Flying half sideways in ground effect over land is not the best place to pickle your external payload if you hope to escape alive, so get over water ASAP and pickle away. On a hot tropical day the air density at low level over water is apt to be slightly greater than over an island baking in the sun. That, plus your now significantly reduced weight should give you a chance to gradually accelerate your "dirty bird" (remember, you're still dragging gear and flaps, and have no hydraulics or electrics) up past VMCa, which will give you better control authority, allow a little relaxation of right rudder pressure (and the use of rudder trim), and maybe if you're lucky, use the last little bit of battery power to feather that windmilling left prop. (Something you should have done earlier, but you were too maxed out.) (Damn those electric props!! If you had Ham Std Hydromatics your accumulators would guarantee full feathering regardless of system pressure or pump delivery volume.)
Now it's time to fly around a bit, get the feel of your plane on one engine with power changes, burn off some fuel, and cuss out the ops officer for giving you (a new guy) this tired old POS, while the new birds with dual everything and redundancy galore went to the senior guys who had more skills and experience, and could have handled this fiasco more gracefully.
Cheers,
Wes

 

[XBe02Drvr]

I remember reading somewhere back in the mists of time that the reason for only one each generator and hydraulic pump was because in this world of American clockwise turning engines, there weren't any readily available accessories of the correct capacities that turned the "wrong" way. Anybody got the straight skinny on this?
Cheers,
Wes

 

[P-39 Expert]

Why didn't they just switch engines from one side to the other making both engines inward turning? Lose one on takeoff and the effects are not nearly as bad.

 

[XBe02Drvr]

Why didn't they just switch engines from one side to the other making both engines inward turning? Lose one on takeoff and the effects are not nearly as bad.

This has been discussed in other threads. That was tried, but it put the entire wing center section in a negative AOA stalled situation, creating lots of drag and no lift, and badly impacting performance, especially in turns and pull ups.
Visualize the slipstream swirling around the fuselages and striking the wing center section, you'll see why. Inward rotation gives you negative AOA; outward gives you positive.
Performance in combat was deemed more important than ease of single engine handling. Calculated risk.
Cheers,
Wes

 

[FLYBOYJ]

Maybe a couple of inches (manifold pressure) away!
Put yourself in the pilot's seat.
Your heavily laden bird has probably stayed in ground lover mode a little longer than usual, so you may already be 10-15 mph into the danger zone before you get airborne. If your left engine quits now, suddenly and totally, your plane instantly starts to swing, and then bank, left. You need to INSTANTLY retard both throttles and STAND on the right rudder with all your might, while shoving forward on the yoke to hang onto the speed you already have. This takes guts, as it's going to feel like you're falling out of the sky, and you will if you don't get a little power back on soon.
Now, if you're fortunate enough to have stopped the turn and you're still flying, you need to find out how much power you can give the right engine without overpowering that rudder and your already shaking right leg. If you have enough control authority to get into a 3°-5° bank to the right, it will improve your performance slightly and give you a better chance of survival. Remember, this all started right after liftoff, and you haven't gained any altitude, so you're probably dodging obstacles to boot, and ground effect is the only thing keeping you alive.
Flying half sideways in ground effect over land is not the best place to pickle your external payload if you hope to escape alive, so get over water ASAP and pickle away. On a hot tropical day the air density at low level over water is apt to be slightly greater than over an island baking in the sun. That, plus your now significantly reduced weight should give you a chance to gradually accelerate your "dirty bird" (remember, you're still dragging gear and flaps, and have no hydraulics or electrics) up past VMCa, which will give you better control authority, allow a little relaxation of right rudder pressure (and the use of rudder trim), and maybe if you're lucky, use the last little bit of battery power to feather that windmilling left prop. (Something you should have done earlier, but you were too maxed out.) (Damn those electric props!! If you had Ham Std Hydromatics your accumulators would guarantee full feathering regardless of system pressure or pump delivery volume.)
Now it's time to fly around a bit, get the feel of your plane on one engine with power changes, burn off some fuel, and cuss out the ops officer for giving you (a new guy) this tired old POS, while the new birds with dual everything and redundancy galore went to the senior guys who had more skills and experience, and could have handled this fiasco more gracefully.
Cheers,
Wes

Hi Wes- great narrative! But you know you're painting a "worse case situation" LOL, but that's what we train for, right?

I remember reading somewhere back in the mists of time that the reason for only one each generator and hydraulic pump was because in this world of American clockwise turning engines, there weren't any readily available accessories of the correct capacities that turned the "wrong" way. Anybody got the straight skinny on this?
Cheers,
Wes

I believe you're correct but to mention again, no one ever thought more than an handful of P-38s were ever going to be built. As pointed out no one properly trained to fly twin engine aircraft, let alone thought about accessory redundancy in 1937. All this was eventually learned.

I believe a gear plate was put at the base of the accessories that were placed on the right side to include the magnetos, but I'm almost guessing about this. I'll have to look into some old books and manuals.