For Bf 109 experts: oil filler hatch

[Roger Gaemperle]

Hello,

The vertical position of the oil filler hatch behind the propeller spinner indicated which type of oil tank was mounted on the Bf 109.

A lower position just on top of the first air scoop indicates a 36 litres oil tank with a horseshoe shape, which is usually associated with the DB 605A or AS.

A higher position (c.20 cm or 6.5 inches over the air scoop) indicates a 50 litres oil tank of annular shape, which is usually associated with the DB 605D.

Now, here is my question: on several Bf 109 G-14 I have seen that the lower oil filler hatch is installed, but interestingly a clearly visible outline of the higher hatch position is present. An example of such a photo can be found in Prien/Rodeike 'Messerschmitt Bf 109 F,G,&K Series - An illustrated Study' by Schiffer Publications on page 160 at the top (Uffz. Gerd Hauter next to 'White 41' of Jagdgruppe Ost). If you look just above the oil filler hatch, you can see part of this outline. It is also visible on several other Bf 109 G-14/AS aircraft.

One theory by me, which may be totally wrong, could be that holes for both the lower and higher position of the oil filler hatch were added to the sheet metal that covered the nose and that during assembly one of them was covered by sheet metal and the other one by a hatch. This way, that nose could accommodate both oil tanks / engine types, which would have made sense from a production efficiency / simplification standpoint of view.

What is the view of the Bf 109 experts out here? Maybe this feature has been known already and there is an easy explanation.

Happy 2015 to all,

Roger

[PhilippeDM]

Roger,

According to JC Mermet, the motor cowling you refer to is from type 041. He add this description: (my translation)
'These are the same cowlings as for type 40 with a DB 605 A engine, but with the big 50 lit. oil tank. This cowling was exclusively used by Bf 109 G-14 with werknummern between 462000 and 464000. Those aircraft were produced by Erla Leipzig in parallel with BF 109 G-10 equiped with DB 605 D engines. This explains probably the use of the big oil tank on DB 605AM engines, to simplify the engine production, to avoid an unnecessary diversification of the accessories delivered by subcontractors'

Clear drawings accompanies this text.

The same occurs to cowling Type 061, where the assembly line uses DB 605 ASM in conjunction with DB 605 AM and two oil filler points are present.

Also to be seen on Type 100 cowlings for DB 605 D engines (Bf 109 G-10 (WNr. 130000); Bf 109 G-10/U4 (WNr 610000 to 613000) and Bf 109 K-4) The oil tank has now a volume of 60 lit. And finally on Type 110 and type 111 cowlings (WNrs between 150000 till 152000 and 490000 till 491000, produced exclusively by Erla, engine DB 605 D.

All those cowling types bear other differences, but I tried to resule the oil tank issue.

Hope this helps.

Source: Mermet, Jean-Claude - Messerschmitt Bf 409 G & K, Editions Caraktère, Hors-Série Aéro Journal N°1 - 07-08/2008

[Roger Gaemperle]

Philippe,

Thank you for your helpful message. So this feature has been known already. The photo I referred to in my first post was most likely produced by Mtt Regensburg, 78x xxx batch and I have found several other example from this W.Nr. range that featured these two holes for both oil tank types.

Best regards,

Roger

[PhilippeDM]

Roger,

I think JC Mermet explanation is very plausible and do not wonder if Mtt Regensburg used same subcontractors for engine cowlings as Erla.

Perhaps new light will be given on the subject in the forthcoming book from JC Mermet Caraktère Publishing covering the Bf 109, to be published later this month....

[one-o-nine]

Hello,

still a miracle:
who invented the designation for the different cowlings in "Mermet-style" as type 40 / 100 / 110 / 111 etc.?

These numbers were never used in any (known) MTT-document or drawing!

[Snautzer]

The authors numbering not mtt according to the article

[schwarze-man]

Sorry to come into this so late! There are complications with the fitting of the different 36l/50l engine oil tanks. The simple difference of the capacity is not a real issue but, the larger tank also gave greater "settling" time and air space to assist de-foaming. The access panel for replenishment also needs to align with the refill point. However, one of the important differences that should be understood is the position of the oil thermostat. The smaller (horseshoe) tank would normally have the oil thermostatic valve fitted in the gap at the top of the oil tank. The larger tank had no space at the top for the valve and, it was generally fitted in a revised oil circuit, near the oil cooler, under the engine. These modifications could also be associated with the installation of the Olschluder (centrifuge-defoamer). Cheers

SM