Why is it upside down???

Dr.VanNostrin · 03-10-2008, 07:27 PM

Hey Fellers!

Here's one for ya! WHY are most German fighter engines inverted? Now keep in mind this question is coming from a real "engine" guy. I've worked on everything from lawn mowers to formula one engines... I can't figure it out. I see MANY disadvantages and not many advantages. So! What do ya think???

Dr.Vnos

To the winner....Your choice of six cold beers!

I'm the judge and jury!! HA!

barkhorn45 · 03-10-2008, 07:41 PM

one advantage is that it would leave more room for the cowl-mounted machine guns that the german fighters carried

GaryMcL · 03-10-2008, 11:47 PM

Another advantage would be putting the thrust line (crankshaft/prop) of a non-radial engine where the designer wants it without having the cylinders and normal top end sitting in the pilots line of sight.

SoD Stitch · 03-11-2008, 12:01 AM

My best guess is this created an engine with a lower center of gravity, putting most of the weight at the "bottom" of the engine instead of the top. It also made servicing the engine somewhat easier, as most of the "complicated" stuff (fuel lines, spark plugs, ignition wires, valve covers, etc.) was at the bottom of the engine, not the top, where it would be easier to get to.

The bad news is this required a "dry sump" lubricatiing system, which is more complicated than a "wet sump" lubricating system.

Dr.VanNostrin · 03-11-2008, 07:30 PM

Very Very Good!!!

You guys are using your heads! The beers may need to be split!

Screw it! Lets all have a few!

Dr.v

Apart from that. I KNOW our German frriends had a very solid reason for putting those zylinders down. I like the servicing idea as well as the gun arrangment. That makes some cents.....It would be nice to hear from some of our experts!' ....Wurger??????? Call your friends.

Take care my friends!!!!!!!

dR.V

Matt308 · 03-11-2008, 08:31 PM

I agree with the low C-of-G argument. There are some visibility considerations too. Look at the Spanish Bf-109s post war.

Aaron Brooks Wolters · 03-11-2008, 08:43 PM

Keeping the crank shaft out of the oil in the oil pan would give a substantial gain in horse power, not sure how much but on a automotive street engine you can gain about 20 horsepower. So a gain of maybe 50 hp could be possible with crank that large. Just a guess.

wilbur1 · 03-12-2008, 10:25 AM

Probably to keep the valves closed so you dont need big a## springs, just let gravity do it

Velius · 03-12-2008, 01:28 PM

Something I've learned from A&P school (which no one brought up here

) is that by inverting the engine you raise the crankshaft above the aircraft water-line. This raise in the crankshaft will raise the propellor as well and if you raise the prop, you can design a plane to use shorter landing gear (thus better forward ground visability)!

barkhorn45 · 03-12-2008, 05:57 PM

apparently did'nt work on bf-109 it's long landing gear and lack of ground visibility on landing lead to alot of accidents

Velius · 03-13-2008, 12:44 PM

True, but perhaps it did shorten what would've been a longer landing gear. The overall design of the landing gear was between the lesser of two evils- a long landing gear or a long-er landing gear.

Makes me wonder, with all the 109 variants why wasn't any attempts made to make the aircraft more stable during take-offs and landings thru the landing gear?

Dr.VanNostrin · 03-14-2008, 06:38 PM

Interesting Guys!

And very good points! I've studied the Jumo 213. I believe one of the main reasons for this configuration is to be able to place a cannon down the center line of the engine. The Bf-109 did this as well. I can't think of any US or English aircraft that did this. So! I still believe that the design of this type of engine must have been tough!

Thanks for your thoughts guys!

Kurfürst · 03-24-2008, 01:39 PM

With the inverted vee, you get the narrower top cowling, translating the better visibility over the nose/sides. Also, you will have your exhaust pipes lower as well, which is a big plus for night flying, the exhaust glare will not blind the pilot during the night sortie so much.

Regarding the cannon installation, its probably not related.

The reason that kept US/English inline aircraft from having an engine cannon was the fact that the supercharger was placed directly behind the engine, ie. being in the way. At least for Merlins this is true, but I believe the Allisons had the s/c right behind the engine, too. The DB engines as you can see have their superchargers mounted on their side.

On the other hand, the engine cannon installation - between the cylinder banks - was successfully done with upright Vee French Hispano-Suiza engines, which sported a 20mm Hispano cannon in the nose, much like the later 109s; Soviet Yak fighters, which in effect used a domestic copy of the same French engine under the disguise of Klimov, also had a hub cannon.

I seem to recall that using direct fuel injection was a great ease for German designers to cope with tech problems arising from an inverted configuration, but it appears it yielded a lot of advantages.

mkloby · 03-24-2008, 02:38 PM

Quote:

Originally Posted by Kurfürst

Also, you will have your exhaust pipes lower as well, which is a big plus for night flying, the exhaust glare will not blind the pilot during the night sortie so much.

Where did that come from Kurfürst? I've never heard anything like that before or experienced that either.

Kurfürst · 03-24-2008, 04:38 PM

IIRC the first Spitfire tests mention its not very good for night flying because of the high exhaust stack. You literally gaze into the exhaust pipes..

You will find that many WW2 night fighters had some sort of a glare shield, or exhaust pipe for that reason (and also not to act as a lighthouse in the darkness..). The Germans even had ammunition with low-light tracers specially for nightfighter operations.