Bloch 152 with -N49 engine

[greybeard]

After having watched the extremely interesting document linked HERE, I wonder what were the true performances of same aircraft with the Gnome Rhone 14N49, especially altitude where it reached its top speed.

 

[eagledad]

I have been looking on the net for years trying to find data on the MB-152 and was lucky to find this. I also was surprised at the low speed recorded compared to the speeds credited for the Bloch. I will continue searching for data on the MB-152 with the 14N49, but have not been successful so far.

Eagledad

 

[greybeard]

... I also was surprised at the low speed recorded compared to the speeds credited for the Bloch.

I found explanation on this article (a few excerpts follow):

"Overwhelmed by a lot of shortcomings, the engine makers were not able to define a cowling which can be aerodynamically efficient"

"A new experimentation of cowling seemed to be necessary, with a diameter of the air intake started from 0.85 m to be enlarged up to 1 m – this being the standard fitting on the MB 151 - and to decrease again to 0.85 m when cooling flaps were fitted."

"With the narrow air intake of the late cowling, fitted together with exhaust pipes and the more powerful GR 14 N 49, the MB 152 prototype achieved a top speed of 515 kph, a jump of 30 kph! A narrower air intake – 0.80 m – was used for the latest operational Bloch fighter, the MB 155."

Please notice also mention to exhaust pipes, since this was the second reason, if I understood correctly, for the difference in performance.


Also helps what written on relevant Profile :

"From early in October 82 machines had been accepted, serials starting from No.301, powered by the more powerful Gnome Rhone 14N49 driving a Chauvière type 371 airscrew. The engine cowling was of the definitive .850 mm diameter; the exhaust collector, copied from that of the Curtiss H75, embodied two outlet pipes at the bottom of the cowling..."

So in short:
1 m diameter engine cowling air intake = 482 km/h
.85 m diameter engine cowling air intake + exhaust pipes = 515 km/h

Records on French document you linked seemingly belong to early model.

I still can't find evidence of altitude where this latter speed was reached, although I can guess some 5000 m or so.

 

[waroff]

Not easy to compare the MB151 & 152 early with 152"late"
The 151 drived a GR propeller variable pitch pneumatic control and 152 drived by a G&R propeller adjustable on ground or a Chauviere in wood fpropeller fixed pitch for ferry flight) and Chauvière série 371 variable pitch in flight..
power max of GR 14N25 (MB151 and 152 "early) and GR 14N49(MB 152 "late")
GR 14N25 : 1000cv at 3600m - 800 mmHg - 2400 rpm
GR 14N49 : 1070cv at 3700m - 800 mmHg - 2400 rpm
(source notice technique des moteurs Gnome et Rhone 14N, 1939)

the MB152/GR14N25 reach 375km/h (IAS) or 458TAS 4000m nominal 2400rpm & 820mmHg
a flight test give 480km/h at 5400m, 800mm Hg and 2550rpm