Douglas C-124 Globemaster II APU?

[Stephan Wilkinson]

Yes, I know there aren't many C-124 warbirds flying around in private hands...but maybe some of you know the answer to this question anyway.

I read here and there that the C-124 was the first aircraft to have an on-board APU, by which I assume they mean a turbine APU capable of starting engines and running plenty of electrical systems, since many 1940s and even '30s large airplanes had small gasoline recip "auxiliary power units."

So my questions are: was the C-124's APU a turbine, and was it the first?

[Randy Wilson]

Hi Stephan - piston engined APUs (then called Auxiliary Engines or Power Units) were in use prior to the end of WWII. The B-29 used such an engine during start up, take off and landing due to most of its system, gear, flaps, etc. being electric. The 1944 issue of "Aircraft Engines of the World" by Paul H. Wilkinson, has a section on American Auxiliary Engines listing ten such engines from Andover, Eclipse, Lawrance and Onan. I hope that is of some help.

Randy

[The Inspector]

We just had a thread about APU's a couple of weeks ago-very intreresting subject and info in there-

[JohnB]

It was a piston "V" twin cylinder, four stroke.
Ther were two...one in each outboard nacelle and could be used singly or together at altitudes up to 10,000 feet.

I have my father's C-124 flight handbook.
You have my email, let me know if you need more...there is three pages on the operation of the APU.

[JDK]

We just had a thread about APU's a couple of weeks ago-very intreresting subject and info in there-

We did. Stephan started that one, too.

[Stephan Wilkinson]

Interesting... On another aviation forum where I posted this same question, a respondent posted a brief Popular Mechanics article, and a photograph, about C-124s having been equipped with "the world's smallest jet engine" as an APU. So I guess the answer is that "some" C-124s had turbine APUs, since you're obviously correct about your father's airplane having two recip APUs.

[JohnB]

Interesting... On another aviation forum where I posted this same question, a respondent posted a brief Popular Mechanics article, and a photograph, about C-124s having been equipped with "the world's smallest jet engine" as an APU. So I guess the answer is that "some" C-124s had turbine APUs, since you're obviously correct about your father's airplane having two recip APUs.

Easily explained. Perhaps.
My dad's POH is dayted 15 July 1955. They could have been refitted with turbine APUs later in the aircraft's career...and they served another 20 years.
Anyone know if that happened? On the other thread someone mentioned that KC-97s were retofitted with turbines....so I guess it's possible...though I'd guess that they might have been relocated or the installation modified because of higher exhaust temperatures.

[Randy Wilson]

Stephan - if you are interested, I scanned the auxiliary engine pages from the book I noted above and made those pages into a pdf.

http://rwebs.net/avhistory/images/wix/US_Aux_Engines_1944.pdf

Randy

[Forgotten Field]

Randy,
Thanks for posting that- I have never seen it before. I have the Andover, an example of each Lawrance, and the Eclipse in my collection. The Eclipse NEG I have has the PTO occupied by a bilge pump- must have been some kind of Seaplane APU.

[Stephan Wilkinson]

Thanks, Randy.

If anybody cares, my strange interest in APUs--this thread and the previous one--is because I'm doing a C-130 piece for Aviation History, and numerous claims about "first APU" are made for the Herk. Which, it's already obvious, aren't true.

Hope everybody enjoys my Zero cover story in the new (July) issue of Aviation History, out momentarily. (God only knows where publishers buy their calendars...)

[The Inspector]

Then don't forget the tale of the Navy digging out of the ice and snow a long abandoned 130 from VX-6 @ Mc Murdo that the Navy wanted back to replace a lost one. The Mechanics dug out the APU compartment, did a partial oil change, hooked up a can of fuel and a battery, pushed the switch and got 'WHIRRRRRRRRR---CLICK_CLICK_CLICK FOOMP! and that little old GTCP 85 lit right off.