Good High Altitude Performer

[schwarzpanzer]

What makes a good high altitude performer?

Was the Me109 the best ever?

I've heard big wings and small wings are good? (e.g. Ta152 former, Me109 latter)

The Me109's specialised for high-alt all seem to have had their wings enlarged though...

Also all seem to have inlines, was the radial at a disadvantage? - or was it just plain horsepower that mattered?

I can't see frontal area as being the problem, considering the Ta152's annular radiator...

I can see underwing air intakes as being a problem, considering they'd reduce lift?

Thanks to anyone who answers.

 

[lesofprimus]

The Ta-152H was the best high altitude fighter aircraft, and if u look past the actual #'s that flew combat at the tail end of the War, it is pretty much considered the greatest prop job of the War....

 

[schwarzpanzer]

IIRC that was the one used to guard the Me262 bases?

So was it good at low altitude too? 8)

 

[Erich]

curious where this myth about the Ta 152H as a Höhenjäger comes from ?

lets try and get this straight shall we !!!!!!!!!!!!!!!

the Tank was never used and I mean NEVER used in airfield protection for ANY Me 262 unit.

the Doras of the Würger staffel all 5-6 of them tired to protect Galland circus JV 44.

the Dora-9's of III./JG 54 did a crap job of protecting Kommando Nowotny.

NO other jet unit ever had a high protection staffel of any 109 nor Fw 190's

thank you for your time, I shall be signing off now ........ 8) hey put that rock down

Schrumpf-Germane

 

[lesofprimus]

curious where this myth about the Ta 152H as a Höhenjäger comes from ?

Not sure, but it does get old hearing it over and over...

the Tank was never used and I mean NEVER used in airfield protection for ANY Me 262 unit.
the Doras of the Würger staffel all 5-6 of them tired to protect Galland circus JV 44.
the Dora-9's of III./JG 54 did a crap job of protecting Kommando Nowotny.
NO other jet unit ever had a high protection staffel of any 109 nor Fw 190's

Yup on all accounts....

 

[MacArther]

Two of my books site that the Kurt fighters were used for Jet top cover, which proves yet another thing that is wrong with my books. First one I noticed, right after I got it, was the statement "The Zero could acieve higher speeds that early adversaries early in the war because of its methanol boost."

 

[FLYBOYJ]

Two of my books site that the Kurt fighters were used for Jet top cover, which proves yet another thing that is wrong with my books. First one I noticed, right after I got it, was the statement "The Zero could acieve higher speeds that early adversaries early in the war because of its methanol boost."

Are they Osprey Books?

 

[KraziKanuK]

Don't remember where I read it but flying the 109 over 30kft was said to be like trying to balance while standing on a tight rope.

Under wing air intakes?

 

[Erich]

probably another mythical statement by W. Green in one of his books. there are so many web-sites attributed to the Fw 190's with Ta 152 specs you cannot even count them as where they got their info is under specualtion except they copied one another or used the same reference(s) to come to their conclusions ............ gag

 

[MacArther]

Actually, they aren't. I'll scan a picture of em, but I think it may be biased because it is coming from an American pilot in a book about American pilots and their opinions on theirs and enemy planes. Even with the allowed bias, this is still absurd!

 

[delcyros]

Some technical thoughts.
High altitude = low air density (low speed of sound) = very cold temperature
So a good high altitude fighter has to overcome these major problems.
It needs to have a low wingload (therefor big wings are better),
some cockpit modifications (the first to name a pressurized cockpit and a reliable canopy defrozing system). Then it needs de-icing or heating systems for the control surfaces and (very important) for the powerplant as well.
Then we have a plane to be physical capable to sail in high alt but it still has no sufficient power and the plane needs time to climb to that altitude ( additional fuel capacity), yeah, introduce some very powerful compressors to the engine in order to keep its engine power output at high altitudes (this increases weight...arggghhh (that´s usually the point when designers get crazy). Not the latest You will have to modify the propeller design (low Speed of Sound= BIG PROBLEM) in order to deal with near Mach speeds at the screwstips.
Some last words on the weaponry: low airdesnity also implies a lower desgree of stability, you will need to factor the recoil forces of guns much more, especially for wingmounted ones...

 

[FLYBOYJ]

Some technical thoughts.
High altitude = low air density (low speed of sound) = very cold temperature
So a good high altitude fighter has to overcome these major problems.
It needs to have a low wingload (therefor big wings are better),
some cockpit modifications (the first to name a pressurized cockpit and a reliable canopy defrozing system). Then it needs de-icing or heating systems for the control surfaces and (very important) for the powerplant as well.
Then we have a plane to be physical capable to sail in high alt but it still has no sufficient power and the plane needs time to climb to that altitude ( additional fuel capacity), yeah, introduce some very powerful compressors to the engine in order to keep its engine power output at high altitudes (this increases weight...arggghhh (that´s usually the point when designers get crazy). Not the latest You will have to modify the propeller design (low Speed of Sound= BIG PROBLEM) in order to deal with near Mach speeds at the screwstips.
Some last words on the weaponry: low airdesnity also implies a lower desgree of stability, you will need to factor the recoil forces of guns much more, especially for wingmounted ones...

Good points - something to think about...

A U-2 at 70,000 has four knots seperating stall speed and maximum safe speed for the airframe. Even at 45,000 feet with a "WW2 high altitude aircraft" you're going to have a similar situation.....

 

[Gnomey]

4 knots is pretty tight, I didn't know that Joe, good stuff. Good points delcyros I'd agree that the plane would have to be a combination of all of thoses (as they still have to be to a certain extent today).

 

[GregP]

A good high-altitude performer had several attributes. Small wings were not among them.

First, in WWII, you needed a good 2 or 3 stage supercharger, or a combination turbo-supercharger with enough of a pressure ratio to give useful power at the altitude of choice. You don't really need a high-output engine, just one that continues to put out useful power at high altitide (the turbo / supercharger).

In WWII, "high-altitude" usually meant 35,000 feet and higher. Some WWII specialty reconaissance planes flew in the mid to upper 40,000 feet range (I think the Ju-86 could get to about 49,000 feet!).

Second, you needed a wide-bladed propeller(s) to move the air. Third, a long, high-aspect ratio wing would be desirable. A shorter, lower-aspect ratio wing could be made to work in relatively straight flight, but one hard turn and you'd fall thousands of feet before you recovered.

A pressure cabim helped a LOT, but was heavy.

The real trick was to get fuel and oil (automotive oil does NOT work!) that could be made to work at low partial pressure, and many American planes were limited by the R-2800 engine because the magnetos lost insulation and leaked spark at about 30,000 feet and higher. They didn't find that out until late in the war. Once corrected, the R-2800 could go much higher. Several otehr engines also had problems at altitude that were correctable, but you needed access to an altitude cahmber to find out what was wrong.

 

[Jabberwocky]

The Spitfire was considered an excellent high altitude plane, but moreso after 1942..

Initially it struggled at high altitude when compared to its main adversary, the Bf-109. However, the fitting of constant speed propellors beginning in June 1940, and the increase in the engine rating of the Merlin II/III in early autumn that year really helped the Spitfire up high. Better props and more engine power were combined with the high lift wing of the Spitfire allowing it climb and turn dominance in the thin air.

Later, when two stage, two speed Merlin 60/70 family were installed, performance at high altitudes took another jump. The tailoring of the supercharger ratios and propellor rection gearing meant that individual engine types could be altered for their roles. So you end up with the suffix 'F' for Spitfires with engines tuned for medium to high altitde, 'LF" for Spitfires with engines tuned for medium to low altitudes and "HF" for Spitfires with engines tuned to high altitudes.

There were several specialised high altitude Spitfires:

The Mk VI, with a single stage, one speed Merlin 47 was a bit of a failure at high alt, capable of just 275 mph at 38,000 feet.

The Mk F. VII was a considerable improvement. Fitted with expanded wing tips and a two stage, two speed Merlin 64 driving a cockpit pressuriser, it was capable of 375 mph at 38,000 feet.

The HF. VII, of which just 16 were built, was specifically designed to intercept high altitude raiders. Fitted with a Merlin 71 it was the fastest Merlin engined Spitfire, capable of 425 mph at 29,500 feet and 410 mph at 40,000 feet. Service ceiling was over 46,000 feet, but one example flown to almost 50,000 feet when it had its cannon, armour and wing
tanks stripped out to save wieght.

The HF. Mk IX was a standard Mk IX fitted with a Merlin 70. It didn't have the pressure cabin of the Mk VII, so more engine power could be devoted to pushing the prop. Lightened and modified HF. IXs made the highest altitude intercepts of the war over southern England. HF. IXs were capable of 390 mph at 36,000 feet in stock form, but were often stripped of around 900lbs of weight to improve performance and climb.

 

[lesofprimus]

Excellent info guys..

 

[schwarzpanzer]

So, you're saying the Ta152's didn't provide top cover then?


KraziKanuK:

Don't remember where I read it but flying the 109 over 30kft was said to be like trying to balance while standing on a tight rope.

I thought the Me109 was good for high-alt?

Under wing air intakes?

My expertise only applies on the ground, but according to Bernoullis' principle the intakes would be better off moved away from underneath, so as to provide more lift?


delcyros:

Thanks a lot delcyros, you've made it seem a lot simpler,

very cold temperature

A higher concentration of Antifreeze?

Less need for cooling?

(The above 2 would cancel each other out?)

Would the radiators be affected by the thin air, then again it is colder, so again - they cancel each other out?

It needs to have a low wingload (therefor big wings are better)

The Ta152 and Me109T other high-alt Me's had them, but what about the Me109?

some cockpit modifications (the first to name a pressurized cockpit and a reliable canopy defrozing system).

Can't believe I forgot that.

Then it needs de-icing or heating systems for the control surfaces and (very important) for the powerplant as well.

High tolerances also?

DFI would be an advantage here, to prevent carb icing otherwise bi-metal flaps be unreliable?

Were these engines crossflow-type?

Then we have a plane to be physical capable to sail in high alt but it still has no sufficient power and the plane needs time to climb to that altitude ( additional fuel capacity)

You have to travel further at high-alt, due to the curvature of the Earth, correct?

introduce some very powerful compressors to the engine in order to keep its engine power output at high altitudes (this increases weight...arggghhh (that´s usually the point when designers get crazy).

Plus you'd need to reduce the CR.

Then add even more fuel, otherwise have a weak mixture.

- Especially with the cold air? (more effective intercooling?)

Not the latest You will have to modify the propeller design (low Speed of Sound= BIG PROBLEM) in order to deal with near Mach speeds at the screwstips.

Now this I am clueless about, anything to do with variable-pitch propellors?

Some last words on the weaponry: low airdesnity also implies a lower desgree of stability, you will need to factor the recoil forces of guns much more, especially for wingmounted ones...

So, nosemounts are a definate advantage?

Would bullets/shells travel faster further in the thin air?

Am I right in thinking (just guessing) that thinner air allows a higher drag factor? (less of an advantage?)

I suppose lower drag is still an advantage?

What I mean is, can air-cooled radials be used?


GregP:

you needed a wide-bladed propeller(s) to move the air

Thanks.

A shorter, lower-aspect ratio wing could be made to work in relatively straight flight, but one hard turn and you'd fall thousands of feet before you recovered.

Thanks again.

The real trick was to get fuel and oil (automotive oil does NOT work!) that could be made to work at low partial pressure

Very thin viscosity oil then?

many American planes were limited by the R-2800 engine because the magnetos lost insulation and leaked spark at about 30,000 feet and higher.

Thanks again, what caused this to happen?


Jabberwocky:

Initially it struggled at high altitude when compared to its main adversary, the Bf-109

Why was this?

The tailoring of the supercharger ratios and propellor rection gearing meant that individual engine types could be altered for their roles. So you end up with the suffix 'F' for Spitfires with engines tuned for medium to high altitde, 'LF" for Spitfires with engines tuned for medium to low altitudes and "HF" for Spitfires with engines tuned to high altitudes.

This is why I think a turbo supercharger would work good, the supercharger works 'till the turbo spools up, then the turbo takes over.


Am I right in thinking that camouflage paint isn't necessary at high-alt? Saving weight, I saw a polished Mustang P51K that reflected the sky and blended in better than a camo job would.


BTW: Has anyone got any objections to me calling Turbochargers, Turbo's and Superchargers, blowers?

- Are all familiar with this Automotive slang?

 

[Twitch]

You all can kick around what was a good high altitude craft but the 109 was not it for sure. Above 30,000 all it took was a quick move to send it sliding off on a wing and a fight for level control before you lost too much altitude.

 

[Jabberwocky]

Jabberwocky:

Initially it struggled at high altitude when compared to its main adversary, the Bf-109

Why was this?

2 reasons:

The main reason was the 3 blade, two pitch propellor that the Spitfire I originally used.

The 109 at the time was equipped with a 3 bladed VDM constant speed prop, which gave it a speed and climb advantage above 25,000 feet over the two pitch unit of the Spitfire. it gave it a higher flight ceiling and better turn and 'grip' at high altitude.

When the de Havilland constants speed 3 balde props were fitted, the Spitfire was transformed at high altitude. Celinig increased by over 7000 feet, speed was up by 20 mph, cruising speed was higher and climb and manouverability were significantly improved. The constant speed unit stripped about 3.4 minutes of the climb to 20,000 feet and almost 5 mintues off the climb to 25,000 feet. Rate of climb didn't drop below 100 feet/minute until 27,000 feet, compared to 23,000 feet with the two pitch propellor.


The other reason was that the DB 601 delivered more power at high altitudes. This didn't really change until the 2 stage Merlins were introduced in the Spitfire IX.

Still, the Mk I/II/V pilots seemed confident that they had the faster and more manouverable plane at altitude. German pilot account seems to hold that the 109F was much faster than the Mk V but outclassed in manouverability. The is probably most true of the F4, but the Mk V and the 109F1/F2 were about even in terms of speed, except down low where the 109 had a distinct advantage.

 

[Erich]

actually the G-6/AS and G-14/AS did surprisingly well in knocking down LSNF Mossies enroute and away from Berlin at night during the fall months of 1944, so yes to be exact it fulfilled the high altitude role quite nicely for the time being until the Me 262 A-1a came about as the supreme Mossie interceptor