HS.12Z-17 Engine

Shortround6 said:

I would guess that the "take-off" power is somewhat equivalent to the US MIlitary power.

Some engines were limited to 1-5 minutes at take-off power, many early WW II American engines were operated at the take-off power settings for their military rating (same rpm and manifold pressure)

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yes but if take off is military power then what is nominal when it also has max continues as well?

tomo pauk said:

I've posted a bit about that S/C here: link

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Szydlowski got some more patents in France during the War, when Planiol had gone to USA (and worked for Ranger). I think the ultimate versions of their supercharger included mobile vanes in the entry AND mobile vanes in the diffuser (outlet), giving a very smooth and flat boost curve.

Hispano-Suiza 12 Y 45 / 49 = Turbomeca S 39 H3 supercharger
Hispano-Suiza 12 Z 17 = Turbomeca DO V 19 C supercharger

So what would be the low gear and high gear power of HS.12Z-17?

Laurelix said:

So what would be the low gear and high gear power of HS.12Z-17?

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The same because its supercharger is 1 stage, 1 speed...

Bretoal2 said:

The same because its supercharger is 1 stage, 1 speed...

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So then the critical alt is 6300 metres?

1150hp at SL (Nominal)
1300hp at SL (Take Off)
1500hp at SL (Overboost)
-
~ 1160hp at 6300m (Nominal)

Laurelix said:

So then the critical alt is 6300 metres?

1150hp at SL (Nominal)
1300hp at SL (Take Off)
1500hp at SL (Overboost)
-
~ 1160hp at 6300m (Nominal)

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Yes, 6.300 m. at 2400 rpm, but 6.700 m. at 2650 rpm... normal for a gear-driven supercharger !

Not quite normal. The supercharger did use adjustable vanes to vary the actual compression of the air in the supercharger so the power required could change and the amount of charge heating could change. Most other superchargers operated on a somewhat fixed compression ratio. Varying rpm did vary things somewhat but a regular supercharger running at a certain rpm was going to give a certain amount of compression to the incoming air and heat it up a certain amount. With this supercharger even at the same rpm the airflow through the supercharger was affected by the variable vanes so there was less compression at low altitudes and more at higher altitudes.
It might not have worked quite as well as was hoped, but a regular supercharger with a FTH of 6000-6300 meters would show a much greater power loss at sea level.

About WEP...

In Dec 1942 Sir Roy Fedden, former Bristol chief engineer, led a team of investigators to chronicle the U.S. WWII aircraft production effort. His report (May 1943)contains the following passage:



This explains how the engine homologation methods varied from one side to the other of the Atlantic : in Europe, since the mid-1930s, most engines were fitted with a limiter (automatic boost controls) which saved the pilot from overtaking boost pressures which could endanger the engine in the event of prolonged use.
In the USA, no limiter, the philosophy of "extra-power" was therefore different, and the WEP concept was unknown to the English, Germans, French and others ...

It should be noted that Fedden does not give any details about definitions and distinctions between WEP, military rating, international rating, and so on ... Its text deals only with approval conditions and type-test procedure.

Regards,

Alain