P-51D overmodelled!

[lada]

im wondering how can someone behind 109 know, if his plane is handling better or not ?

Anyway if 109 usualy did dive in dangerous situation, how were they initial dive acceleration compare to Pee ?

[Staga]

Ilmari Juutilainen (MT-222 in game was his plane) had to escape from russian Lavotchkins after he run out of fuel.
He dove straight down from 6500m (~19000ft), speed exceeded 950km/h (+590mph) at low and surprisingly plane flew "rock steady". Pull-out was done with trimming wheel thought.

[Angus]

Pretty much what an old 109G pilot also told me....up to 1000 kph would be able for pull up via trim.
But did early 109's have an elevator trim? They did not have a rudder trim at least.
BTW, the same pilot stated that the P47 could easily dive with the 109 and quite faster,,,,,as close to mach as it would go. His conception was that at some dive angles the P47 was up to 200 kph faster than the 109. That means that the 109 was  getting cought pretty fast indeed !!!
At those speeds, the 109 would roll no more, where as the P51 and P47 would. The Spit IX+ would also roll, and pull up without trim even, but a good range behind though.

[Staga]

All 109s had elevator trim thought the trim-wheel moved whole vertical stabilisator (kinda like "flying tail" in jets); not just elevators via trim tabs.

[Morpheus]

this thread is stupid

[Angus]

so, a gear-up rather than a trim-up?
if it works as well, it's just fine!

[IronDog]

Just read a book by former pony ace named Loving.He said he preferred the P51B,because its wing was thinner,as the the P51D's wing was thicker to fix the machine gun jamming problem.
Loving said the P51B handled better,and he didn't miss the two extra MG's.
I guess them old pilots had no idea how there planes flew different,are if the wing was different are not.I'll bet there isn't one guy flying AH that actually flew a P51.Us wannabe fighter pilots should stick to our fantasies,and respect the guys who actually did the real flying and fighting.
IronDog

[Widewing]

Originally posted by IronDog
I'll bet there isn't one guy flying AH that actually flew a P51

You will lose your money.

My regards,

Widewing

[dtango]

A few thoughts:

P-51 wing geometry:
The P-51 wings were based on the NACA/NAA 45-100 laminar airfoil.  There are some slight differences betwen the B and D model wings primarily being that the B model leading wing root extension was enlarged in span and the chord re-cambered to produce the D wing.  The result is that the P-51B's root t/c ratio at (15.2%) is higher than that of the P-51D (13.8%).  

This data comes from Ed Horkey, chief aerodynamicists for the P-51 and calculated by Dave Lednicer and Ian McGilchrist in a 1991 AIAA technical paper.

This is in direct contridiction to the pilot accounts listed above.

B vs. D canopy:
Modern CFD analysis on the P-51B/D shows that there is a strong region of suction across the bubble canopy of the D model not existent for the B model.  If memory serves me correctly the strong region of suction indicates greater pressure differentials meaning a higher possibility of shockwaves forming on the bubble canopy.

This would tend to support the pilot account listed above regarding the D model canopy possibly contributing to experiencing compressibility on the D model.

Other factors:
Couple of other variables need to be considered when comparing pilot accounts about dive issues with the P-51 variants.  According to America's Hundred Thousands, horizontal tail failures were occuring due to directional instability until forward spar of the stabilizer was strengthened in late 1944.  This probably affected D models more than B models because of the greater instability of the D models until dorsal fins were added to the D's.

2ndly the addition of the aft fuel tank shifted the CG of the Mustang and created dangerous instability as well where in a high speed dive a pullout would result in a stick force reversal resulting in wing failure.  Early B models didn't have the aft tank while the D models came with them meaning the D models would more likely experience this problem.  Of course this condition only existed when the aft tank was filled and disappeared as the tank was drained in flight.

3rdly the Mustangs with fabric covered elevators would experience porpoising at high speed due to fabric bulging that would cause elevator oscillations.  This was corrected by installing metal covered elevators and occured as modifications during the war.

These things could account for the reasons for some of the accounts listed above as changes occured in production models of the P-51 from B to D as well as modifications that occured in the field.  Depending on when this occured for a particular squadron pilots within that squadron would probably have different experiences or things to say.

In conclusion, I'd say that there's some misconception and some truth in the pilot accounts above while the experiences could be explained situationally.  In other words there isn't data from the statements above that says the P-51D's flight model in a dive is wrong in AH.

Tango, XO
412th FS Braunco Mustangs

[dtango]

Widewing:

You're absolutely right about Irondog's bet .  A former squadmate of the 412th FS has.

Here are the Mustangs SE (screaming eagle) has access to and has flown.
http://www.mts.net/~lcymbal/index.html

Tango, XO
412th FS Braunco Mustangs

[lada]

well HT its up to you.

take some bread butter, sleeping bag and travell somewhere where you can try dive in 109

[moot]

Isn't IronDog Dlamb?

[IronDog]

I'm not dlamb.Just old AW'er,flying under new cpid.

[Widewing]

Originally posted by dtango
B vs. D canopy:
Modern CFD analysis on the P-51B/D shows that there is a strong region of suction across the bubble canopy of the D model not existent for the B model.  If memory serves me correctly the strong region of suction indicates greater pressure differentials meaning a higher possibility of shockwaves forming on the bubble canopy.

This would tend to support the pilot account listed above regarding the D model canopy possibly contributing to experiencing compressibility on the D model.

According to NAA test pilot George Welch (noted in his log book), the reshaped canopy of the P-51H substantially reduced the elevator buffet experienced with the P-51D/K. This high frequency buffet added to the discomfort of diving at speeds above 0.77 Mach. In no way did this buffeting put the aircraft at risk, it merely introduced a high frequency "buzz" to the stick, which unnerved some pilots. This buzz discipated as speeds further increased. However, all P-51s would demonstrate a severe empanage buffet approaching 0.86 Mach (as demonstrated by Borsodi). According to Horkey, the damping designed into the Mustang's elevator was sufficient to control unwanted elevator excursions below 0.84 Mach. Above this, tail buffet rapidly increased up to 0.86 Mach, where prolonged exposure could lead to structual failure. Borsodi performed his dive tests from 40,000 feet. Below 20,000 feet, the Mustang could not attain such high Mach speeds. Many pilots got cold feet as soon as they felt the onset of compressibility. This was especially common among pilots who "cut their teeth" on the P-38 (prior to the P-38L), which was genuinely dangerous to dive at steep angles from high altitudes.

An simple example of the above described aerodynamic "buzz" behavior is watching your car's sideview mirrors blur at very high speeds.

Bud Anderson has frequently stated that he preferred the P-51B/C to the D model due the earlier fighter's better stability and general handling qualities. He was, however, not especially intimidated by the onset of compressibility.

My regards,

Widewing