Bf 109 F series

[GregP]

Here is a pic of where the Hispano engineers put the cannon port. We have covered it with sheet metal to save weight since the USA frowns on civilians flying armed aircraft AND the intent is to mimick a Bf 109, not an Ha.1112 Buchon.

You can see the slat just outboard of the cannon port. It is retracted in the pic, but air pressure extends it when the plane nears a stall angle of attack. I can get a slat-extended pic if anybody wants to see it.

 

[GregP]

I also said we restored and ran a WWII pulsejet. Here is a clip of it pushing my truck down the runway at Chino. I am the guy behind the driver seat in the truck bed. I started the pulsejet and the primary restorer, Robin Scott, is the guy who steps up and puts the engine into high thrust mode from the idle mode start, and then sits on the trailer.

Robin was the primary force behind the resotration and I helped along the way. He flies a red Yak-52 in airshows when he isn't bored and plays jazz guitar for a hobby away from flying and restoration. AND has cold beer. What more can you ask?


View: https://www.youtube.com/watch?v=KTv7dfs_Mlc

 

[stona]

Very nice images.

Here's a drawing of the main gear attachment on a Bf 109 E, from the parts list, to compare with the first image.

Very similar (as you'd expect).

Cheers

Steve

 

[jim]

Mr GreqP
Nice photos. Thank you for posting them
I would like to ask you this. What internal changes has the wing in order to fit the 20mm cannon? Have the spaniash holed the wing s main spar?

 

[cimmex]

The Spanish 109 had a complete new wing with two spars to hold the cannon. This pic is from meiermotors who is currently restoring a Buchon.
cimmex

 

[GregP]

Checked the manual today and the landing gear toe-in is not specifed, as I expected. Since the drag drag link is cast into the gear leg and is not adjustable, I suppose there is no point in specifying it.

When we repaired the wing damage after the groundloop, we removed the outer wing fuel tanks and the pic above is accurate ... the spar has a hole in it but is strongly reinforced as you can see.

 

[GregP]

Hey Civetone,

In case you liked the pulsejet, here is a short video looking down the throat of the engine while it is running, You can hear this thing for about 10 miles and we scared the crap out of the poor woman in the Cessna 152. The main thing I like about it is you can see the reed valves working ... sort of. The frequency is about 43 Hz, so the sound really carries.


View: https://www.youtube.com/watch?v=U-xlttsfWn4

And here is one of a short evening run:


View: https://www.youtube.com/watch?v=j4hBwCDRwK0

We only have two sets of reed valves and so we don't run it for more than about 1 minute and 20 - 25 seconds. We stop when the pipe temperature reaches 1,100°F or so. When it does, the reed valves are not really all that hot. So with maybe 40 runs on it we have about 25 hours on the reed valves and they are in good shape since we don't run them until the melt.

Unfortunately the unit is down right now for something as mundane as the fuel pump. We need to take it out and get it rebuilt, but the museum doesn't want to fund it ... and we already have enough of our own money in the engine as it is. The cowling you see is home-made and we spent several thousand dollars reproducing the rubber diaphragm for the fuel controller (had to make a mold at a machine shop ... the original had turned into rubber dust).

So ... when they want to run it again, they'll have to rebuild the fuel pump ... it started grinding and leaking and raw gasoline around a hot pulesjet is a formula for an explosion that nobody wants to be around.

Interestingly we can run it on 87 octane or 100 Low Lead but the needle valve settings are different. It seems to prefer 87 octane which it what was used in them in WWII. When we have correct fuel pressure, it strats and runs very reliably.

This is what it looked like before we restored it:

This is what it looked like when we first got it to run:

And this is it when we finished. Same trailer .. .we restored that, too.

The little wire-like thing coming out of the bottom of the cowling running back for a foot and half or so is the thermocouple we use to monitor pipe temperature. That's Steve Hinton's P-51 in the background.

OK, back to the Bf 109F!

 

[wheelsup_cavu]

I had never seen those before restoration pictures.
After seeing them it makes the accomplishment of getting it running all the more impressive.


Wheels

 

[Civettone]

It seems to prefer 87 octane which it what was used in them in WWII. When we have correct fuel pressure, it strats and runs very reliably.

Greg, I always read that the pulsejet was loved because it was able to run on much inferior fuel quality.

Also, how do you assess the vibrations? It is said that the vibrations were too much for the Me 328. But, maybe that's an unlucky matter of oscillations??


Kris

 

[Milosh]

Is that an Argus engine Greg or the American copy as used on the Loon?

 

[Shortround6]

Thank you for all the pictures. They do help in understanding the layout and construction.

 

[GregP]

The engine is a US engine, not an esact copy of the Argus, and was used on the Loon. The US pulsejet is smaller and produces good thrust. We were amazed that the addition of the cowling increased the thrust by 30% or so and we all figure it was the shaping of the cowling that helped direct better airflow into the intake.

Interestingly, forward speed seems to have an effect since we only got to some 15 - 20 mph and the thrust went up another 15% or os even with that slow forward speed. We have a force transducer on the test stand and we get a direct thrust readout, which we calibrated with a canbrated spring. We used a spring with 70 pounds per inch of force (±1%), compressed the spring two inches and adjusted the transducer to get 140 pounds of readout thrust.

We'd love to restore an actual Argus and get it running, but we don't HAVE one. The hardware would be essentially the same. You can see two fuel nozzle lines in the video and the Argus has three. So we MIGHT need 1/3 or slightly greater fuel pressure and flow, but it runs the same as the US pulsejet. We have carefully compared the Argus diagramns with what we see in our pulsejet, and everything is similar.

There IS a real Argus at Chino, but it is in the Yanks Air Museum. not in the Planes of Fame. They have great displays and some really interesting aircraft, but don't fly their planes or operate their display engines. So, we're left with our pulsejet ... when someone wants to pay to overhaul the fuel pump, we can run it agains easily. We KNOW how it works by now and how it starts and transitions between idle and working thrust.

The vibrations are a bit brutal. It goes from full thrust to almost zero thrust about 43 times oper second and you can really feek the vibration ... but not for too long. The heat generated, bot radiant and infrared, is intrense. When you stand right next to it to set the fuel controller, it gets painful rather quickly just from heat.

The German Argus was about 1/3 or maybe a bit less large and the frequency should be a small bit less, say 2 - 5 Hz or that ballpark, but the vibrations would be slightly larger in amplitude and slightly longer in duration. We designed a small aircraft to be powered by the pulsejet we have, but is was a paper design using Lanxair wings and new fuselage. We did the basic desgn, but did NOT do any vibration investigation bevause the Museum would not sell us the pulsetjet or let us try to fly it. Ergo, it would have been a waste of time on our part when beer was available and calling. However, if we manage to get it or one like it, the design could be revived easily and the analysis could be continued.

There were two of us working on the design, me and the primary restorer. The design was basically his and I looked into stress and weight. We KNOW already what a completed Lancair wing weighs since we have a friend who made one and we weighed the wings, complete with control linkages. The fuselage would have been aluminum with a fiberglass nose cone with streamlined fixed landing gear. It would have looked like a miniature He 162 sort of (with the twin tails) only with low-mounted Lancair wings. The intent was to keep it as light as possible while being able to handle 6 - 7 g's in a 5 minute show routine.

 

[bobbysocks]

Well, that kinda knocked me off my feet. Because I distinctly remember this well known website about Finnish experiences with the Bf 109:
virtualpilots.fi: 109myths

And I am talking about empty weight, based on official German test report sheets. Of course the G-6 gained more weigth.

Kris

check this site out... WW II ACE STORIES

 

[bobbysocks]

just remember when you are modding a plane you are still at the mercy of the other technology of that specific time. so if you move the gear outward or put a second spar you will add significant weight to the same aircraft with the same engine. you will most likely lose performance just like they did with the G model. so what are you really gaining? nothing. also, yes, you can probably stick a fuel cell aft of the pilot but what happened when they did that to the 51s?? you had to limit your maneuvers until it was emptied down to ~25 gallons. this they could do while heading to the RV. if jumped right away with a full center tank....would be no fun. the same thing would happen to the 109 if you did that. it would have to be a small enough tank to be emptied when they reach alt. you would be way better off with drop tanks. you can burn all the fuel you want but when the fit hits the shan you can dump them and maneuver like you need to.

 

[GregP]

Hi Bobbysocks,

I get the fact that many out there are strongly resistant to changes to the Bf 109. In real life it didn't change much except to get heavier.

It WOULD have had I been in charge, which I wasn't. Since it is a "what if," I think my suggested changes would have resulted in a better airplane.

Anyone and everyone is free to feel otherwise. But if I couldn't improve the Bf 109, I wouldn't be much of a designer what with the poor sideward and downward visibility, stupid langing gear, extremely short range, poor control feel at higher speeds, and limited stick leverage. I think Willy could have easily improved it, too, but simply didn't for one reason or another, We are unlikely to find out why not at this late date and the few left are certainly better off staying stock in msueums and the few flightworthy examples remaining.

 

[silence]

So, then, since Willy wasn't going to make changes, what could be done in the field? I like the Galland special with the 13mm MGs and little bumps. I also understand that the 601E used 87 fuel; why not tune it up for C3 and increase the boost pressure (I think that's what the change would be useful for - please correct me if I'm wrong!)

And which was the last unit to use the F? How long into the war did it soldier on?

 

[bobbysocks]

greg, i am not resistant to change or improvement. i am sure there are things that could have been done to the F series to get the most out of that airframe / engine combo. like others have said its rob peter to pay paul for the most part. whats it going to gain you vs is it really worth it. a retractable tail wheel and cleaning up of the air frame....removing any possible bump ( with the exception of a rear view mirror), seam, high standing rivit, etc. ...having gear doors that completely cover the retracted gear....no fabric used at all.... could have netted you a little more speed. rudder trim and some way ( possibly a more complex or compound system of pulleys ) to boost flight controls at high speeds IF the airframe could take that degree of stress. experimenting with vortex generators and ways to lower the stall speed...many turning battles were fought in the edge of stalls. ways to boost and cool the engine with existing space restrictions. better vis with a better designed hood. drop tank / bomb rack. experiment with different size wings and styles of wing tips....experiment with manually operated standard flaps instead of slats...which would require moving the radiators <<<< so that would be in the mix if it could be done in a more aerodynamic way. some of these may be impossible to impliment but i would have a go at it.

as for the design of the u/c...yeah its not ideal but get over it. if you're a pilot you learn to fly it. i dont see any data...other than the mythical rantings quoting ungodly high numbers that no one can prove... that the LW suffered significantly more accidents during landing DUE TO AIRPLANE DESIGN or PILOT ERROR than the allies or other axis contries. i have a bunch of pictures of 51s with that wide gear ....cracked up on a field without battle damage....it is what it is and they were all about the same. und das ist meine zwei Pfennige wert....

 

[GregP]

We already know the airframe can take a good deal of stress. Speed doesn't change the ultimate strength of the structure. If it can take, say, 7 g, then it can take it at any speed that is under the flutter speed. Since Bf 109's were involved in many, many diving attacks, I feel pretty safe in saying the flutter speed was high. The Bf 109K could hit 450 mph and possibly slightly faster. To have a safe margin, the flutter speed should be higher than 500 mph, so it isn't an issue.

I don't believe they were about the same and I do believe the Bf 109 had more than its fair share of ground accidents due to the gear. The stall speed was low and the takeoff run was short. They operated out of farmer's fields.

I don't have to get over anything, I like the Bf 109. The thread evolved along the path of what could be done to improve it and I went with it. Nothing more. One change I'd definitely make after watching some combat film is to change from 3 wing mounting points to four. That way, if ONE failed for some reason, the wing woudn't fall off as it was otherwise prone to do. I'd also change the windscreen as a minimum into something MUCH better.

That's two changes I'd make for sure, even if it interrupted production for a short time in addition to adding rudder trim. Of course, I'm also not running Messerschmitt ...

As for what could be done in the field, the answer is almost anything. They had the normal tools for repair and such, but also had fabrication tools for repair of battle damage. That being said, they did NOT have metal casting facilities, so major changes would be tough but doable on a one by one basis ... if there was ample proof of need for the changes. Apparently there wasn't as I haven't seen a lot of pics of field-modified Bf 109's.

We had and have to do fabrication to restore our Hispano, the YP-59A, and the pulsejet, but we also have sent some things out to local shops who specialize. Maybe those jobs could be done in the field and maybe not. Most field mods are done for the sake of necessity, such as fitting more fuel for a special mission. They don't usually engage in field redesign whout getting into some trouble with the powers that be.

So, I'd lean toward most field mods being of the repair and special fitting for specific mission type of mods in the real world.

So possible changes are one thing and likely changes are another ...

 

[OldSkeptic]

Greg I think the 109 (at least the E anyway) had very good positive G limits but poor lateral ones. From memory I remember reading that pilots (again in the E so not sure this applies to the F) were warned to not get any yaw or side slip in a dive otherwise they could overstress the airframe.

As for field modifications it is amazing what they could do at times. The great story of the RAF's ME Command modifying a Spit V to get the high altitude performance to take out JU-86Ps is a classic of its kind.

But back to the F (as I have said that I think was the epitome of the basic design) , the problem is that when they need more engine power and firepower the airframe was just too small to encapsulate them, hence the G 'Bulge', which meant the originally excellent aerodynamics were severely compromised so that the G never really delivered the performance the basic design potentially had.

Though the German engine manufacturers can take some blame for going towards 'make it bigger, rather than more boost' route.

Hence the 'lengthen it' argument for a post F model. Longer nose for the later larger engines, but a longer fuselage to maintain balance (plus the added advantage of some more room for extra fuel, power boosting stuff, etc). Naturally the weight goes up (and the 109 was always the lightest in its class in the European theatre) hence the 'bigger wing' as well.

 

[GregP]

I pretty muich agree, Oldskeptic.

It would not have hurt to be a bit bigger and could easily have helped a LOT. But ... the basic F airframe could have had several things fixed without much weight gain or much effort. Among those would be windscreen and canopy (might actually be lighter), gear toe-in (NO weight gain to fix the wheel alignment), rudder trim, and a bit of exra fuel.

It also would not have taken much to change to 4 wing-mopunt points from 3. They already had the design from the main spar. They only had to make another one and the weight gain would be quite small ... probably no more than 40 - 50 pounds total for both fuselage and wings. Many more pilots would have gotten home.