Boeing B17 Electrical system

[Tony Mabelis]

One of my apprentices (a German!!) informs me that the B17 (by my understanding is considered an 'electric aircraft' as compared with the B24, an 'Hydraulic' aircraft) did not have a 'ships battery', but had a small twin cylinder? engine (APU) driving a generator of some sort to start the Powerplants, and therfore be the only emergency back up in flight.

I find this very hard to accept, can anyone enlighten me (or possibly him!!)

[Atcham Tower]

The small engine was known as a "putt-putt" (from its sound, of course) but I believe they were also fitted to B-24s. An early form of APU, I suppose.

[Tony Mabelis]

The big question is wether the aircraft had a battery

[742]

My father’s B-17G Field Service Manual shows three 24 volt, 34 Amp hour batteries. Number 1 is in the leading edge of the left wing inboard of # 2 engine, and numbers 3 and 4 are in the leading edge inboard of engine # 3. There is no battery # 2; perhaps it was in earlier airplanes?


For what it is worth each engine had a 200 amp generator.

The APU appears to have been for ground use only. Also some were not permantly installed, these had to be removed from the airplane and run on the ground as a GPU.

[Tony Mabelis]

May thanks for that 742,
I have never seen an aircraft fitted with a generator that didnt have a battery in the system.
Your information makes me feel much better, and I will have pleasure in correcting him!!!!

[NutherA2]

I have never seen an aircraft fitted with a generator that didnt have a battery in the system.Phantom FG1 (F4K)