P-51D "Lou IV" and pilot lost

[barit1]

Fatal torque roll (http://www.ntsb.gov/ntsb/brief.asp?ev_id=20070720X00970&key=1) on first solo.

At one time I estimated that the unbalanced torque transmitted through the engine mounts of a Merlin was 5000 lb-ft. and that the available P-51 aileron control moment could be exceeded easily below 90-100 kt IAS.

Sad loss of plane & pilot.

[Agaricus bisporus]

Tragic loss of an irreplaceable airframe.
Think of the scores, maybe hundreds of rookies who handled their first trips in this piece of history without wrecking it. Many only had a handful of flying hours before successfully coping, and then going right into combat...Over the last 55 years! How many must there have been?

But losing control due to well known torque effect on a go-around? Well, maybe, maybe not, but if so what instructional technique allowed that? Cos no way is that the aeroplane's fault. If so shame the instructor wasn't aboard too... Still, if you have to that, do it in Cessnas, not Mustangs! Please!

[barit1]

If the student had 100 hrs of T-6/Texan/Harvard time, as was the case with most P-51 transition pilots, I doubt that this would have happened. Most pilots of that era recall the T-6 (AT-6) taught them the most about flying, and was the best possible transition into higher performance ships.

[proplover]

Agaricus bisporus - shame on your comments. Yes many did cope with the additional torque of the Merlin however many didnt even back in the 40's and 50's. Your comment that the instructor should of been in the aircraft as well brings you no credit at all.

barit1 - you apparently are aware of the unfortunete pilots history with regard to his previous experiance - if not dont speculate. The T6 route whilst expected is not the only way into the cockpit of a P51.

As far as I can recollect with books to hand is the LouIV was not a TF51 ie two lots of controls therefore Im presuming the 'student' must of carried out the initial landing, quite satisfactorily. The instructor could have only been advising as he would have had no input on the controls. This would not of been his first landing so again I presume the 'student' must of demonstrated some ability before being sent 'solo'.

The Stalion51 company is a good example of a controlled training enviroment and I know of several pilots who have taken advantage of it, one of which has less than 5 hrs T6 but is still an extreamly competent P51 pilot.

Remember someone died here, in horrible circumstances in a very public way.

[barit1]

I did not invent the T-6 connection, nor do I claim any great experience in the type, nor do I suggest it's the only way to prepare oneself for the Mustang.

I'm only pointing out the historical fact that a great majority of military pilots came to fly the P-51 via the T-6 (AT-6) route, and the ones I've talked to had high regard for the preparation it gave them. Therefore - based on this proven sequence of instruction - I conclude that this pilot probably would have benefitted from a similar syllabus.

[tinpis]

He was the owner of a T-6

[Blacksheep]

Yes many did cope with the additional torque of the Merlin however many didn't even back in the 40's and 50's. A big difference between now and then is that military pilots didn't buy their own way onto high performance single seaters.

RAF military pilots of the 1940s were streamed into single seaters or multi-engine during basic flight training on Tiger Moths or Magisters, with single seat pilots going on to Harvards and multi-engines going on to Ansons. The fact that high performance single seat fighters could be a handful was well recognized and those who it was thought wouldn't hack it, were weeded out very early in the proceedings. Of those who made it all the way through flight training, only those with the best responses and finest control touch went onto single engine fighters. Even then many were 'chopped' from the course and never reached a squadron.

This policy remains in place to this day. Fast jet jockeys and 'pie eaters' are sorted out very early in the training process. In today's civil environment, if you can afford a part share in on old 'warbird' you can buy into the training to fly it and there's no 'chop' in these circumstances. Its a fact that not everyone has what it takes to fly a single seat fighter aircraft - vintage or new.

[Brian Abraham]

One persons view
http://www.avweb.com/news/pelican/pelicans_perch_87_killer_go-arounds_195755-1.html

[barit1]

Couldn't agree more with the article. Some airplanes can be flown "by the book" with relatively little technique required, and can be taken off, flown, landed and waved off by procedure only. But WWII (& earlier) vintage aircraft demanded a degree of "feel" or technique that is apparently often overlooked in flight instruction today.

My father instructed in all the SE trainers of WWII, and go-arounds were always practiced at a safe altitude to drill home the pecularities of the type. A T-6 or even a BT-13 would quickly roll inverted if full power were applied over the numbers.

I could make an analogy to playing a musical instrument; you can't write a procedure for playing a trumpet or violin. It's a matter of practicing the technique. Some people will "get it" and some won't. :uhoh:

[ShyTorque]

Twenty years ago I flew with a very clever RAF navigator - I found out he had in fact written much of the information contained in the Navigation part of the RAF's Air Publications.
One day, he mentioned that he had once been a trainee RAF pilot but had withdrawn from training. Another time, after a few beers, he told me why.
He was night flying the Balliol T2 trainer (Merlin engined) when, during a low and slow go-around, it did a 720 degree torque roll for him and scared him half to death, although he escaped without crashing. He decided that someone was telling him something..

[Dick Whittingham]

Ref Brian Abraham's link, my first thougt would be that at low rpm and full boost you would get more torque than at higher RPM.

As to the T6, I trained on them and instructed on the less powerful (400hp?) Piston Provost. Over one year I do not recall any accidents at our T6 school caused by torque roll, nor do I recall any problems personally. The one time I had to slam to full power was in a PP at very low IAS and I got much more yaw than roll.

Mind you, our Canadian instructors, with time on Mustangs, did consider torque roll to be a killer, but there you are talking 2000hp.

Dick Whittingham

[NutherA2]

the less powerful (400hp?) Piston ProvostFrom my Provost T.!. Pilot's Notes, Dick:

INTRODUCTION
The Provost T.I is an all-metal, low-wing monoplane
powered by a 550 b.h.p. Leonides 126 engine driving a
three-bladed, constant speed propeller.

This was in the good old days, when we were allowed +8 lbs boost :) and I believe it gave us the same bhp as the Harvard.

[Dick Whittingham]

Old men forget, Nuther, but I have the figures for the Harvard, 600hp @ 2250rpm. I liked it, its only snag was wing drop in the stall, particularly in manoeuvre

Dick W

[tinpis]

Face it...some folks would never get the hang of a Piper Cub.

[Brian Abraham]

Dick Whittingham - If I'm reading the Merlin 22/24 power chart correctly, at sea level and 1800rpm max boost was +6 giving 675HP. At 3000rpm max boost was +18 giving 1620HP.

The formula is
Power(hp)=torque(ft.lbs)*rotational speed(rpm)/5252

I'll let you do the maths. :8

As an aside, before we went to the carrier for the first time the instructors showed a vid of prop operations on a carrier. One spectacular sight was the F4U's launching and immediately rolling in 60° of left bank on leaving the deck. We thought it just a little of the macho showing, but instructors advised it was torque in control and pilot was just along for the ride until a bit of airspeed was gained, and hence aileron control.

[kiwi chick]

Face it...some folks would never get the hang of a Piper Cub.

Yet again, well said - and so true.

(Tinpis - I am in great admiration of how you manage to speak my mind, but with about 150 less words than i would have used... ;) )

[barit1]

The formula is
Power(hp)=torque(ft.lbs)*rotational speed(rpm)/5252

The only thing I can add is that it's the prop shaft rpm that's of concern here; thus one needs to know the gearbox ratio to find prop rpm. My recollection is that it's about 0.4 gearing (i.e. rpm is about 1200).

(Note for the skeptic: crankshaft torque is reacted within the gearbox; prop torque is reacted in the engine mounts) :8

[Dick Whittingham]

Corrct, barit, and Brian is talking about reduced boost in cruise conditions. The point about torque reaction on TOGA is that it is going to be at high boost, and under those conditions reducing RPM means that torque reaction will go up. Or look at it this way. At max boost and max RPM if you pull the prop lever back to reduce RPM you are setting a coarser pitch. This will generate more torque drag on the prop. Of course, reducing RPM may force a reduction in ehp, but not necesarily on the engine's ability to produce torque. Where do you get max torque in your car?

We need more numbers!

Dick W

[barit1]

Performance curves can usually be found in the engine TC reference data or acceptance criteria; I can't say I've seen any for the Merlins but someone doubtless has them in a bin somewhere.

And you're right about torque going up if a lower rpm is set - In fact that's how the prop governor is able to control rpm: it varies the load torque absorbed by the prop.

But shouldn't the old GUMPF check mean the prop is set to high rpm on approach? That does two things: 1) adds a bit of drag by placing the blades in flat pitch, and 2) makes for less to worry about on a touch-&-go or a waveoff.

[Dick Whittingham]

The last thing I want to do is challenge a 38,000 hour pilot who has flown a Bearcat and survived, but I do not agree that it is better to set less than max rpm in preparation for a landing - because you need may need max rpm for the unintended abort. Barit is right about the drag on finals - good thing - with fully fine. We both think John Deakin has it wrong about the torque at lower rpm. I think, from my limited experience that mixture rich and prop to full fine are two checks that should be done downwind at the latest.

IMHO the real way to avoid torque stall incidents is to govern your throttle hand. It is self evident that the aircraft will have aileron authority to keep wings level at all flying speeds or the pilots notes would limit power permitted at low speed. Torque stall comes from an imbalance on the rates of application of power and aileron and rudder. It is a handling problem.

Dick W

[Brian Abraham]

Perhaps an explanation lies here. The USAAF manual lists 45" as the normal take off boost (but a max of 61" is available) and I would assume a civil owner would want to take care of his machinery ie use the 45" in the normal course of events. The go around procedure like wise calls out Advance throttle quickly but smoothly to the normal take off manifold pressure of about 45". Caution: Don't jerk or jam on the throttle. Avoid sudden bursts of power. Use all controls smoothly.

Maybe in the heat of the moment he made use of some of the extra 16" available and explored what to him was unknown territory.

[barit1]

Since my curiousity was piqued regarding the Merlin gear ratio, I did a bit of search and find two different ratios (or more?) were in use. The standard for the P-51 installation was apparently 0.479:1 - and the document I found is most interesting! See: http://www.caa.co.uk/aandocs/22231/22231000000.pdf

[Brian Abraham]

The Mustang used a number of different versions of the Merlin as follows.
Merlin V 1650-3 with a gear ratio of .477, the -7 and -9 ratio .479
The -3 and -9 had the same supercharger drive ratios (6.391/8.095) as well where as the -7 were different (5.802/7.349). Naturally this meant that all three engines had different power ratings.