Did Enemy Have Compression Problems?

[Dadtallica]

I compress a 109 at least once a week. 

[SIK1]

No - the P-47 and P-51 were the same, limit dive speed. Both were placard restricted at 0.75, both 'do not exceed at 0.8M. IIRC the max dive attempted and survived by P-47 was 0.83M. 0.85M for P-51D;

The P-47C and D made holes in the ground just like P-38s for the same reason, just a little higher threshold for the aft movement of Center of Pressure that caused the infamout 'mach tuck'. Both were more or less solved by P-38J and P-47D-30 (IIRC) installation of dive flaps.  The P-51 never had that problem due to he unconventional nature of the 45-100 airfoil.

The dive flap both moved the CP forward when deployed, and reduced the acceleration of the extreme turbulence that blanked the elevator authority.  The P-38 while also having wing mounted dive flap also moved the CP forward whe deployed but while it redced mach tuck, the centerbody was still blanking the elevator - but pilot 'got relief' anyway because the dive flap introduced a pitch up (small but important-both P-47 and P-38).

Great explanation. 

I read some accounts of P51 pilots, switching from P51B to the D model, experienced problems trying to dive after the German planes, they experienced problems due to the bubble canopy.

The early 51 D models had some stability issues because they had less side area due to the removal of the turtle deck. It was resolved with the addition of the dorsal fin.

 
Sik

[icepac]

I explore all flight models at all altitudes.   
If you don’t you miss out.

[drgondog]

Great explanation. 


The early 51 D models had some stability issues because they had less side area due to the removal of the turtle deck. It was resolved with the addition of the dorsal fin.

 
Sik

The 'reduced side area'due to installing the bubble canopy is a myth.

The RAF/R-R discovered the yaw instability immediately after Merlin installed in Mustang I. AL 963 was modified with both a dorsal fin,then increased chord fin/rudder combination. The issues and flight test results were reported to NAA in Feb 1943. NAA tested the dorsalfin o the P-61B-1 and NACA tested both he DF and a tall tail in fall 1943. InMarch 1944,both the DF for P-51B and P-51D  were released to Service Group for kit production, but the P-51D production article was only released for P-51D-5 (both Inglewood and Dallas) at #651, and for last block P-51C-10-NT.

The additional benefit to streamlining flow during yaw, increasing effective fin/rudder area - was reduction of torsional loads on empennage in yaw due to prop vortex.

[Brooke]

I remember reading an account of a 109 pilot who got into compressibility trouble.  I don't remember the reference, though.  I recall him, in desperation, deploying some amount of flaps during the dive, too.