There are original documents from March 1945 about the difficulties of the Ta 152's flight stability and the proposals to improve it. The extent of this issue is not very well-known I assume.
On the German Flugzeugforum the member and owner of the docs Junkers-Peter posted them. You have to sign up on the forum to see them though there:
www.flugzeugforum.de
Here is a translation into English I made.;
"Both the first production aircraft of version H and the model aircraft of version C have insufficient stability over the longitudinal and lateral axis.
As an immediate measure, the head of TLR therefore decided to reduce the fuel supply by 70-80 liters. and the entrainment of only 70 liters MW 50 instead of 100 liters suggested (this only with regard to the longitudinal axis?)
The head of TLR was subsequently informed that in order to achieve perfect stability around the transverse axis in the first series aircraft (H), it was necessary to attach approx. 58 kg of ballast to the engine and the fuel content of the rear tank of 360 ltr. to be restricted to 280 liters.
However, it is not possible to attach the ballast to the engine.
Chief TLR therefore proposes not to install the GM-1 installation, especially since the proper functioning of the pressurized cabin is still in question. The ballast on the engine and the fuel restriction could then also be omitted (in this case).
A meeting with the E-Stelle (Test Center) Rechlin showed that this proposal by the head of TLR would, in the opinion of the E'Stelle Rechlin, not be a remedy .
The E-Stelle also stated: The vertical axis stability of the 8-152 H is just sufficient. However, according to the shooting school, shooting approaches are not possible. A slight improvement occurs with the help of the course (direction) control K-23.
Rechlin suggested a different stretch (aspect-ratio?) of the fin to Focke Wulf as a remedy and sketches for it were handed over to Focke Wulf.
Transverse axis stability is poor for both C and H.
In principle, these instabilities around the transverse axis can be eliminated by:
Abandonment of course control K-23
Abandonment of GM-1 installation
Abandonment of 115 liters tank
Abandonment of FuG 185
Reduction of the fuel supply by 135 ltr.
Such a waiver, not even the smallest reduction in the fuel supply, can under no circumstances be approved!
In addition, when carrying out these measures, a top-heaviness near the ground would have to be accepted.
Fundamental measures were discussed:
a) Enlarging the horizontal stabilizer by adding edge caps
b) Modification of the wing transition to the fuselage to achieve better flow conditions
c) Engine pitch forward 0.5° further
d) Try to move all the weights further forward if possible
e) to compensate for the ballast of 13.5 kg previously required in the rear with a wooden tail
An aircraft with the above difficulties is unusable for troop deployment.
A complete remedy seems possible only with fundamental means."
On the German Flugzeugforum the member and owner of the docs Junkers-Peter posted them. You have to sign up on the forum to see them though there:
Fragen zur Dora/152
Korrekt, Peter. Ich habe Fotos von den Beschussversuchen. Die wurden in Frankreich durchgeführt. Wenn gewünscht, fotografiere ich die mal flink ab. Ein (!) guter Treffer mit 30mm Mine reichte, um einen Bomber abzuschießen.
Here is a translation into English I made.;
"Both the first production aircraft of version H and the model aircraft of version C have insufficient stability over the longitudinal and lateral axis.
As an immediate measure, the head of TLR therefore decided to reduce the fuel supply by 70-80 liters. and the entrainment of only 70 liters MW 50 instead of 100 liters suggested (this only with regard to the longitudinal axis?)
The head of TLR was subsequently informed that in order to achieve perfect stability around the transverse axis in the first series aircraft (H), it was necessary to attach approx. 58 kg of ballast to the engine and the fuel content of the rear tank of 360 ltr. to be restricted to 280 liters.
However, it is not possible to attach the ballast to the engine.
Chief TLR therefore proposes not to install the GM-1 installation, especially since the proper functioning of the pressurized cabin is still in question. The ballast on the engine and the fuel restriction could then also be omitted (in this case).
A meeting with the E-Stelle (Test Center) Rechlin showed that this proposal by the head of TLR would, in the opinion of the E'Stelle Rechlin, not be a remedy .
The E-Stelle also stated: The vertical axis stability of the 8-152 H is just sufficient. However, according to the shooting school, shooting approaches are not possible. A slight improvement occurs with the help of the course (direction) control K-23.
Rechlin suggested a different stretch (aspect-ratio?) of the fin to Focke Wulf as a remedy and sketches for it were handed over to Focke Wulf.
Transverse axis stability is poor for both C and H.
In principle, these instabilities around the transverse axis can be eliminated by:
Abandonment of course control K-23
Abandonment of GM-1 installation
Abandonment of 115 liters tank
Abandonment of FuG 185
Reduction of the fuel supply by 135 ltr.
Such a waiver, not even the smallest reduction in the fuel supply, can under no circumstances be approved!
In addition, when carrying out these measures, a top-heaviness near the ground would have to be accepted.
Fundamental measures were discussed:
a) Enlarging the horizontal stabilizer by adding edge caps
b) Modification of the wing transition to the fuselage to achieve better flow conditions
c) Engine pitch forward 0.5° further
d) Try to move all the weights further forward if possible
e) to compensate for the ballast of 13.5 kg previously required in the rear with a wooden tail
An aircraft with the above difficulties is unusable for troop deployment.
A complete remedy seems possible only with fundamental means."
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