The Inertial Starter on the Messerschmitt Bf 109

[Broncazonk]

It's interesting how this aircraft was started. Notice how the battery cart spins up an inertial starter instead of merely engaging a starter motor? The inertial starter has a starter motor attached! (Has to be a weight saving design feature, no?)

https://www.youtube.com/watch?v=hQpVpV2sUM8

Bronc

[schwarze-man]

This starter uses the electric motor, spinning-up the inertia flywheel to about 18,000rpm. This is then engaged to the rear of the crankshaft (with a very high reduction ratio gear). The German versions were licence-built from the American "Eclipse" company. German Bosch modified and adapted the original design to produce a whole family of these inertia starters or, Schwungkraftanlasser. They were the primary type of starter system used by Luftwaffe aircraft in WW2. Contrary to popular writing, the wartime Bf109 types did not use the electrical energised starter. There was no room behind the DB engine on the 109 because that was where the ammunition magazines for the MG15/131 or the MK108 were fitted. The wartime Bf109 was only fitted with the manual-only AL/SED starter which was short and fitted into the gap. However, most of the modern rebuilt 109's with the real DB engines have been fitted with the electrical version of the inertia starter because the owners do not care enough about originality to use the manual-only correct starter. This modification also requires considerable redesign of the electrical wiring and use of non-original types of starter switch. This is unfortunate as, manual only operation of the starter is not difficult. The type of starter used on these modified hybrids is usually the Bosch AL/SGC electric type that was used on the Bf110 and other larger types with the DB engines.

SM

[schwarze-man]

Bronc,
Thanks for posting that video. The take-off on that vid is very unsatisfactory. The engine appears to be running at low power and the aircraft hardly accelerates. This could have been due to poor pilot technique, an incorrect propeller setting or some other problem? The engine seems to perform much better later in the video. Overall, I am pleased that it did not end as a wreck.

SM

[Snautzer]

Or because of trail flight not maxing it out but a more conservative use of available power ?

[schwarze-man]

Hi Snautzer,
I do not know why this take-off was performed like this so that is why I can only observe what is on the video.
There is a whole load of experience of operating the real 109 today and, there should be no reason to use such a risky technique. The engine should have been fully tested on a test stand or in the airframe. Even brand new there is no restriction on using 1.3ata/2600 for getting airborn and this gives a very sprightly take-off. I have video of our 109 getting airborn in 5sec from a stop, putting power on using this power setting.
Watching this video (linked above), I cannot really tell if the low power, full length takeoff roll is deliberate?
Can I suggest we start a new thread if you would like to discuss 109 handling?
Cheers

SM

[Snautzer]

S-m i am certainly not an expert like yourself on this. I thougt it logical not to use max power in 1 st flight. However your logic about testing etc is (unlike mine) ofcourse flawless. Thank you.

[schwarze-man]

You are correct that a new engine would not be operated at max power and, there is a program of operating at fairly low power for the first few hours. However, normal maximum (1.3ata/2600) is available for take-off if required.
Ground testing of the engine should have covered most of the running-in anyway. We did 5 hours of ground running before flying. The engine can be run to full power with the tail anchored. This was great experience and I ran the engine to full 1.42/2800 for testing, although the aircraft only normally used the 1.3/2600 in flight. Cheers

SM

[Broncazonk]

So just to be clear, there were no battery cart starts for this aircraft during the war--they were all started by the hand crank. (Did I read that correctly?)

Here is video of the electric inertial starter procedure from inside the cockpit.

https://www.youtube.com/watch?v=wR8SOB1Fmbg

And here is an electric inertial starter powered by an internal battery.

https://www.youtube.com/watch?v=5nj7...eature=related <-- This man knows how to fly the airplane.

Bronc

[schwarze-man]

Originally Posted by Broncazonk

So just to be clear, there were no battery cart starts for this aircraft during the war--they were all started by the hand crank. (Did I read that correctly?)

Here is video of the electric inertial starter procedure from inside the cockpit.

https://www.youtube.com/watch?v=wR8SOB1Fmbg

And here is an electric inertial starter powered by an internal battery.

https://www.youtube.com/watch?v=5nj7...eature=related <-- This man knows how to fly the airplane.

Bronc

Hi Bronc,

Yes, all Wartime Bf109 fighters were started by mechanical hand-crank of the Inertia starter, AL SED. A German battery cart might have been used to power the radio and instruments etc when the aircraft accumulator was unservicable or flat. However, NO wartime production 109 had the electric energised starter as original equipment.
Your two videos here show: first, my old friend Charlie Brown flying the G-12 conversion with DB605. You will see at the engine start that he uses what should be the electrical isolation switch to contact the electrical supply to the electric starter because, they have fitted a non-standard electrical starter and have used the isolation switch as a supply to the electric motor on the starter. I do not know exactly how they have wired the electrical isolation switch to work this way, I suspect that it is wired just as a switch to the electric motor on the starter but, the German aircraft that did use the electric/inertia, like Bf110, Fw190 and larger aircraft, had a special starter switch that also switched the current to the motor. Also, the main current was contacted through relays and a circuit with a auto circuit breaker. The 109 has non of these extra electrics for a electric starter motor as original.
The second video shows Walter Eichhorn flying the great FMBB. Here, I think that this aircraft has a larger accumulator fitted and modifications to the electrical system allow the use of the electrical-energised starter. Not original.

SM

[Snautzer]

Originally Posted by schwarze-man

You are correct that a new engine would not be operated at max power and, there is a program of operating at fairly low power for the first few hours. However, normal maximum (1.3ata/2600) is available for take-off if required.
Ground testing of the engine should have covered most of the running-in anyway. We did 5 hours of ground running before flying. The engine can be run to full power with the tail anchored. This was great experience and I ran the engine to full 1.42/2800 for testing, although the aircraft only normally used the 1.3/2600 in flight. Cheers

SM

Hope you made some recordings (sound and moving) for this, i would love to see them :-))