Gnome-Rhone air cooled engines.

[Landos]

Hi All,

I'm a new poster in the forum so I ask your patience if I'm posting on subjects that have been extensively discussed in the past.

I'm curious about the performance of Gnome-Rhone series of air cooled fighter engines, such as were used in the Bloch MB152 and PZL-24 series of fighters. I've heard the later models of these engines (1000 HP and above) had overheating problems. Anybody have the skinny on those type of issues? Were they ever resolved? Anything else you can tell me on those engines?

Thanks!

[Civettone]

Yes, overheating problems of the 14N were overcome later on. Needed higher grade alloys though.

14R still had problems but these too would have been solved had the French continued working on them after the armistice.
Kris

[Landos]

Thanks Civettone.

[Arsenal VG-33]

In researching your query, I came upon two books - My Rand McNally Encyclopedia of Military Aircaft says very little on the MB 151-155 series planes saying only that it had poor performance at high altitudes. However, I recently found a book I had since childhood called, "French Fighters of WW 2", Hylton Lacey, #11. In the chapter dealing with the MB 151-155 series fighters, there is mention (pg. 20) of 2 experimental prototypes.

One called for a 1,200 hp Pratt & Whitney R-18300S3C-G Twin Wasp 14-cylinder two-row radial engine to be installed in the MB 153 frame. Filght tests in April 8, 1939 showed performance to be about the same as with the original French engine (Gnome-Rhone 14N25).

There were also plans for a 1,200 hp Wright R-182 Cyclone 9-cylinder radial to be installed in the MB 154 frame. The engine was not delivered before France fell in 1940.

During the occupation, limited testing was allowed under the German occupational authorities on the MB 156 (MB 152 airframe but re-engined), but this was abandoned and instead a redesigned frame would be adopted for a more powerful engine. This would be the MB 157 powered by the Gnome-Rhone 14R giving 1,590 hp at take off, or 1,700 hp at 26,000 ft. (pg. 25)

Testing in 1943 showed the aircraft to have excellent qualities and performance. However, the Germans were more interested in the engine and took it back to Germany, leaving the airframe in France, where it would be destroyed in an Allied air raid in 1944.

The more I read about this unfortunate plane, I realized that the French government was close to cancelling the MB 151 project in favor of more modern designs (the D.520 for example), but the looming threat of war convinced them to allow the production series to continue. This is too bad as a cancellation of this project it may have helped streamline existing production lines on the more modern aircraft and producing more of them.

The heating problems with the MB 151-155 series occured mostly within the oil unit, and the airframe was modified several times to allow for a ventral cooling duct for the oil system. The undercarriage and cockpit was slightly modified on several occassions as well. Overall, a lot of time and money was spent on this aircraft that otherwise would not have been necessary on the other designs at the time, and had the threat of war (and perhaps politics) not been present, in all likelyhood this plane would have never left the prototype stage in 1936 and been cancelled then and there.