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.

[Mr Schmitt]

Interesting reading. Attached images are the said hand starter.


Happy New Year to all.

[schwarze-man]

Many thanks for posting those images of the Bosch AL SED AR1 Anlasser Mr Schmitt!
As can be seen, this starter is the manual-only type, that was used by the wartime Bf109. The reduction ratio from the flywheel produced around 800ftlb's of torque on the 3 toothed engagement dog. You can see that this particular starter has seen some use, with the dog teeth showing some damage. Cheers

SM

[Broncazonk]

At the end of the wind-up, it looks like you had to get the handle out in a hurry or you would end up with a broken arm--the handle would continue to spin?

Video of a wind-up inertia start on a D13 @ the 5:03 - 7:00 min. mark:
https://www.youtube.com/watch?v=uf7nyTdwsHU

Video of a wind-up inertia start on a D9 @ the 23 sec. mark:
https://www.youtube.com/watch?v=4Y5LBUVS1T8

Also, the process looks exhausting. I can't image trying to start these things in the blowing snow, at 20-below zero F. on the Ost front.

Bronc

[schwarze-man]

Thanks for posting those vids Bronc.
The 109 in that first vid is a Hispano airframe with a genuine Bf109E engine and cowling and some unknown type propeller blades. I guess that they also fitted an electric energised type starter and rigged it up but, I don't think it was working correctly.
The 190 is the rebuilt genuine D-13 with the Jumo213. This should have the electrical energised starter as standard and they are using the manual back-up for most of the video as it is not working correctly.
Overall, the manual or electric inertia starter is reliable when used on a servicable aircraft.
Cold start, there is a proceedure for using the inertia starters in cold conditions. The DB605 came with oil dilution and acetylene gas cold start equipment as standard.

SM