Power used by auxiliary equipment?

[tomo pauk]

...ie. the pumps, generator etc? How big was part of the piston engine power that got consumed by the necessary auxiliary stuff?

 

[davebender]

AI radar added weight, took up space and consumed a considerable amount of electrical power.

AIA. Single seat fighters such as F6F and F4U.
1,050 watts power.
310 lbs.
Requires removal of two machineguns and reduces top speed by 2mph.


SCR-540. Installed in Beaufighter and A-20.
1.1kw power.
210 lbs.


SCR-720. Installed in P-61 night fighter.
3kw power
412 lbs.

Night fighters also had additional communications equipment, navigation equipment, receivers to home on enemy radar etc. Plus a crew member to operate all this stuff.

 

[tomo pauk]

Thanks for the input; my point of interest here is the engine stuff, though

 

[Shortround6]

The engine "stuff" doesn't take anything away from the rated power. The oil pumps, coolant pumps and some of the fuel pumps are already figured in (or out?) by the "brake horsepower". Power available at the shaft. The engines don't need generator to run although the plane needs a generator. Vacuum pumps, air pumps, hydraulic pumps do take power to run but aren't needed by the engine. They too are airplane system requirements and do not run all the time.
The Post war Hercules engines had a 150hp accessories drive although I am not sure they ever used the full capacity. This might have included allowances for a cabin pressurization blower. Early P-40 Tomahawks had a number of problems with generator drives, in part because initial testing was done with a 500 watt generator and then the British specified a 900 watt generator minimum but actual bought 1500 watt generators for installation. Bombers or transport planes could easily require much more auxiliary power than a fighter and a number of multi-engine aircraft had APUs installed to handle the loads.

 

[tomo pauk]

I know that engine auxiliaries dont's 'take' any HP from "brake HP"; was just wondering how much engine power was needed to power all what needed to be powered
Thx for the info.

 

[Shortround6]

There is no break down but one figure for a V-1710 Allison is 147hp at 3000rpm for internal friction and internal systems, pumps and drives but not including supercharger. Please note that the Friction HP could vary quite a bit from model to model depending on piston ring tension, valve springs, width of internal gears and such. late model, high power engines also used different pumps. early C series engine could move 125lb/min of oil while a late model G series could top 200lbs/min. coolant flows also varied.
I can't find much more at the moment.

 

[Rivet]

One facet of ancillary systems that popped into my head, though not related to engine power diversion, was the use of externally powered electrical generators. This particular to German construction practise. Pilots of the Me-163 and Ju-87 mentioned that the drag of the devices propeller, as well as the centripedal forces, tended to steer the aircraft at high speeds.

I recall reading some papers done on the topic of engine power losses by NACA. I believe the author was Weick, though not certain. It's been a while. Oil viscosity figured in the investigation. Both the U.S. and a U.K. site have the papers internet available. Regards

 

[tomo pauk]

Thanks for the additional info

 

[FLYBOYJ]

Folks, just for the record, all this stuff is actually refered to as "accessories."

 

[Shortround6]

While a generator,vacuum pump or hydraulic pump may very well be an accessory I believe that oil pumps and coolant pumps are necessities, but then I am not a mechanic

 

[tomo pauk]

Joe, thanks for reminding me - superchargers are also accessories? IIRC the engine-driven superchargers were consuming up to 200-300 HP for Merlin-sized engines?

 

[FLYBOYJ]

Anything bolted to the block either directly or though an accessory case or gear box that turns by being driven by the engine is considered an accessory. Depending on the manufacturer or installation, the supercharger too would be considered a separate accessory. Sometimes superchargers carry their own logbooks, I do know APUs do.