Spitfire IX/Merlin 61 at high altitude

[HoHun]

Hi everyone,

I just found some information relevant to the topic below which I took from a recent monster thread (http://www.hitechcreations.com/forums/showthread.php?postid=1229708&highlight=pressure+spitfire+altitude#post1229708).

From Duncan Smith, "Spitfire into Battle":

"One of the greatest thrills was having twelve Spitfire Mk IXs in battle formation at 43,000 ft in the knowledge that no German fighter could touch us."

(You might have seen that quote before.)

"In fact, the limiting factor rested in the flying equipment available to do the job because existing oxygen and ventilation sytems could no longer be considered entirely efficient to meet the exacting conditions. Without pressurisation at such great altitudes, the physical discomfort from fatigue and pain from 'bends' limited the flight-time we could endure to barely five minutes or so."

(Two paragraphs down from the first quote. I think this highlights nicely why the race for altitude was finally abandoned!)

Regards,

Henning (HoHun)

---cut-------------
Hi Angus,

>Oh, and HoHun, you're right. Spitfire IX with a Merlin 61, my mistake calling it a HF.
>It is good at high altitude none the less.....

Roger that! I'd say it represented the peak of the race for altitude :-) For some reasons, that race was abandoned shortly after the introduction of the (Merlin 61) Spitfire IX. The Luftwaffe had geared up for production of the Fw 190B, which would have been the high-altitude Focke-Wulf with suprisingly good performance up high, but canceled it right before it was to go on the production lines. Subsequent Spitfires got engines designed for lower altitudes, and the P-51 swapped its high-altitude Merlin for a medium-altitude one, too.

I'm not sure what the reasons were for this paradigm change - it might be that stratospheric flight without pressure cabins was fairly dangerous in itself, even before you ever met an enemy up there.

Regards,

Henning (HoHun)

[Angus]

Hello
Nice.
I once talked with a pilot who took a Spitty up to 49000 feet. I asked him if it had been uncomfortable, and he said "not really"
Getting to 49K he would have exceeded those 5 minutes by far in the alt bands above say 35K.
The cold peaks before 30K he said, and as a sidepoint, he found it to be colder in the high alt bands over the med than i.e. over Britain.
I do recall some pilots mentioning it being painful to keep flying that high, joints started aching etc.
This particular pilot mostly hated long escort missions (P51) cruising at 30K+ for hours (5 hours or so I think), those were the really cold arse missions he said. The ride was P51.
A Spitty would never be up that high that long, so I wonder how it worked.
The human body does not instantly submit to lowering pressure, it comes a bit gradually, as you'll know, your legs will swell more on longer flights etc.
Also, I wonder what being arse cold did as an effect, well, it slows down your bloodstream (veins schrinking) but that again slows the effect of low pressure.

Anyway, there is another factor with the super high flying that has not been mentioned yet.
The aircraft were not that tight, and going viciously between alt bands woud "Ice" the whole interior, the windscreen included.
Surprizingly, many aircraft never had a cure for this, - Gunther Rall mentions scraping Ice in his 1944 model 109G.
Some Spits had a cure in the form of a little tube from the outside to the windscreen, keeping it free, but those were  field mods (1942 onwards). I wonder about the US planes. At least they incorporated electrically heated suits for high flying and some more gadgets.
Anyway, would be nice to know more.

[Crumpp]

Angus,

From what I know, in order to reach extreme altitude in an unpressurized environment you have to pre-breath 100 percent oxygen at sea level.  

It is kind of like SCUBA diving in reverse.  By breathing the O2 at the higher pressure of Sea Level your body off gasses Nitrogen.  There is a table very similar to Dive tables in that it gives the amount of time you must breath O2 at sea level to reach the target altitude.  It includes a time limit at which you can stay at that altitude.

Cold makes you more susceptible to decompression sickness.


Crumpp

[HoHun]

Hi Angus,

>I once talked with a pilot who took a Spitty up to 49000 feet. I asked him if it had been uncomfortable, and he said "not really"

Hm, that's 15 km. Are you sure he had no pressure cabin or at least a pressure suit?

http://www.dfrc.nasa.gov/Research/AirSci/ER-2/pshis.html

http://www.astronautix.com/craft/wiltsuit.htm

>The human body does not instantly submit to lowering pressure, it comes a bit gradually, as you'll know, your legs will swell more on longer flights etc.

I think there's a lot of variation between individuals and even for the same individual depending on the varying level of fitness and adjustment. The 5 min certainly aren't edged in stone, but if you wouldn't need pressure cabins, why was so much effort put into them?

I found the following article quite interesting:

http://www.avweb.com/news/columns/182156-1.html

Just as airmen of WW1 ignored the dangers of high altitude flying when they went up without oxygen, WW2 pilots climbed beyond safe altitudes, too. To a certain degree, it paid off because it gives you the altitude advantage, but cruising routinely at unsafe altitudes can add to operational attrition exceeding the tactial advantages. It's my impression that this point might have been reached in 1942, reversing the trend towards ever higher altitudes.

>The aircraft were not that tight, and going viciously between alt bands woud "Ice" the whole interior, the windscreen included.

The windscreen was actually affected worse, because it was a big block of armour glass that wouldn't adjust its temperature quickly. I think this problem was shared by all contemporary aircraft as I've also found it mentioned for US planes. A fresh air tube could mellow the symptoms, but not entirely prevent it either. (From what I've read, British test pilots liked the effective Me 109E ventilation, but of course without a sliding hood, it better should be effective :-)

>At least they incorporated electrically heated suits for high flying and some more gadgets.

I think the Luftwaffe had these, too, including electrically heated gloves which made operating the cockpit switches much easier. Eric Brown thought these compared favourably to the fur-lined British gloves "guaranteed to turn your fingers into a bunch of bananas".

As far as I know, heated suits were standard equipment with Bomber Command, too. I seem to recall that one crew member had a malfunction of the regulator and was left with the choice between frost bite and burns, eventually suffering the latter despite his attempts to adjust the temperature by cycling the suit between on and off all the time. (I'm not entirely sure on the RAF bit, though, it might have been the story of a USAAF crewman after all.)

>Anyway, would be nice to know more.

Yes, fascinating topic only seldom mentioned in the books! :-)

Regards,

Henning (HoHun)

[thrila]

I'm guessing it was probably a spit VII that got to 49,000ft (pressurised cabin).

[HoHun]

Hi again,

Another interesting article from Deakin:

http://www.avweb.com/news/columns/182123-1.html

Have a look at the GLOC paragraph.

Regards,

Henning (HoHun)

[Angus]

Nice links.
Got to give me some time for reading here.
For the 49K Spit, my memory sais IX, but I'll have to get to log books to verify. I am pretty sure it was not a pressurized cabin though.
That pilot flew Mustangs on longe range escorts to Berlin,- for the RAF, - P51C. They never got anything electrically heated and were basically freezing their butt off on those missions. He mentioned that they were always being promized heated gloves and suits etc, but never got any, unlike the Americans.
About that Oxygen status, I am a bit confused.
13K is often stated as a DO NOT GO HIGHER WITHOUT OXYGEN alt.
Well, once upon a time I climbed up to 12K and cruised there for an hour or so without noticing a thing. (Cessna 172). So, definately not chopped in stone I must say.
And I live at the humble elevation of 60 feet..........

[Crumpp]

Yep,

The reason you prebreath is to prevent decompression sickness not Hypoxia.


 

About that Oxygen status, I am a bit confused.

The USAAF says 12,500 feet is the O2 cut off.  Above that you must me on Oxygen.  This is because the symptoms of Hypoxia can be insidious.  

It is similar to Nitrogen Narcosis when SCUBA diving.  I used to have students taking a Deep Diving Specialty do math problems at the surface and time them.  We would then go to 130 FSW and do the same problems.  On average it would take 5 times as long for them to do the math at that depth.  Many of them would swear they felt nothing but the stopwatch told the real story.

Crumpp

[Guppy35]

The generally accepted highest combat in WW2 was the interception of a JU86R over England by a specially modified Spitfire IX flown by Emanual Galitzine. where he managed to get to 44,000 feet.  Galitzine wore an electrically heated suit btw.

I don't believe that the 49K story is accurate as I don't know of any Spits that got up that high, pressurized VIIs or not.  The absolute ceiling on a Spit VII is 45,700 with the service ceiling 45,100.

Needless to say the physiological affects on pilots in unpressurized cockpits at those high alts was extreme.

There were some locally modifed Spit Vs in the Med used to chase JU86Ps and those pilots really struggled, and they didn't reach those altitudes as the single stage Merlins just couldn't do it, although they did manage to stop the Ju86P sorties.  This of course led to the R model which could get to 45K

I'm a Spit fanatic, and have even had the pleasure of corresponding with and meeting Galitzine a number of years back, but that being said, I don't believe any Spits made 49K

Dan/Slack

[gripen]

The high altitude performance competion was at altitudes where the high altitude bombers (B-17 around 30k)  and reconaisance planes flew (Mosquitos, PR Spitfires etc. again something around 25-30k). Generally pilots were not asked if it was comfortable to fly at high altitude; the task was up there so they flew there. Some planes had pressuriced cabins, most not.

The next Merlin used in the Spitfires after the Merlin 61 was the Merlin 63 (reached service at spring 1943) which offered about same high altitude performance as the Merlin 61. Later HF Spitfires got the Merlin 70 which offered actually better high altitude performance than the Merlin 61 or 63.  And some amount of HF Spitfires were produced alongside LF variants until the end of the conflict.

The Fw 190B was basicly the Fw 190A with the GM-1, seems that one of the prototypes had a larger wing but otherwise the Fw 190B offered quite little imrovement over the Fw 190A at high altitude and the Bf 109G with GM-1 did better so the was not much reason to produce Fw 190B. The developement of the Fw 190 (with BMW 801) was going towards multipurpose fighter use and high altitude developements were continued under designation Ta 152 from late 1942 onwards (which all featured new larger wings as well as other engines). The Fw 190D was, according to Kurt Tank himself, a stop gap solution until the Ta 152 reached production and actually late Fw 190D variants were multipurpose planes again.The only real high high altitude version of the BMW 801 to reach limited service was 801J of the Ju 388, otherwise the high altitude performance of the BMW 801 was quite limited even with the GM-1.

The Germans or Focke Wulf never abanoded race for high altitude performance, they were just unable to field their high altitude piston engine developements; the Ta 152H was too little too late, most other piston engined high altitude developements were failures.

Regarding the change from the V-1650-3 to V-1650-7 in the P-51. This was decided at autumn 1943 because USAAF had allocated all P-51Bs to tactical fighter use and RAF also wanted medium and low altitude performance. All P-51 developements after the P-51D (P-51F, P-51H etc.) featured high altitude engines and actually some late P-51Ds got V-1650-9 too. Still even with V-1650-7, the P-51 did better than most german fighters at high altitude.

gripen

[MiloMorai]

Gripen, if the P-51B was assignd to the tactical role, then why was there still Bs flying deep into Germany with the 'heavies', a year later?

[gripen]

Originally posted by MiloMorai
Gripen, if the P-51B was assignd to the tactical role, then why was there still Bs flying deep into Germany with the 'heavies', a year later?

The whole story can be found from the "P-51Mustang: Developement of the Long-Range Escort Fighter" by Paul A. Ludwig. The first unit in the ETO to receive the P-51B was the 354th FG of the 9th AF, the second unit to receive it was 357th FG of the 9th AF. The Mustangs were allocated for 9th AF (ie a tactical AF) but the crisis in the day light offensive late 1943 forced USAAF to think again and so these units were assigned for escort task with known results. Basicly USAAF had allocated it's best high altitude fighter for tactical purposes.

gripen

[Widewing]

Originally posted by gripen
Basicly USAAF had allocated it's best high altitude fighter for tactical purposes.

gripen

Well, many would argue that the P-47 was the AAF's best high altitude fighter. However, it lacked the range to be its best escort fighter. That role belonged to the P-51. You are correct that the AAF assigned the Mustangs to the 9th Tactical AF. Standard bureaucratic stupidity. It was typical of the AAF to assign by squadron availability rather than by aircraft type. Once Gen. Arnold became aware that the P-51 was the answer to deep escort needs, most Mustangs went to the 8th AF Fighter Command. By late 1944, only the one 8th AF fighter group flew anything but the P-51 (56th FG flew P-47s throughout the war). P-38s and P-47s were transferred to the 9th Tactical AF where their superior durability and load lifting capability could best be exploited.

As it was, the 8th AF managed to get the first P-51 groups placed under 8th FC control. Virtually all of the new P-51s arriving in Britain were immediately assigned to 8th AF groups. The 4th FG flew its first P-51 escort missions with some pilots having less than 10 hours of Mustang flight time. On the job training, so to speak.

The overwhelming problem faced by the Luftwaffe, beyond a shortage of trained pilots and decreasing stocks of fuel, was the fact that the 8th AF now possessed a fighter that could loiter over Luftwaffe fighter bases, effectively ending the ability to rearm and attack the bombers on their return flight. For many Luftwaffe pilots, the most dangerous portion of the mission was simply getting back down on the ground without being shot out of the landing pattern. This was an especially effective method of cancelling the advantage of the Me 262. Germany could and did disperse their fighters all over the countryside. However, this greatly impacted command and control, as well as general logistics. As the British and American Armies advanced nearer the German border, things only got worse as the shorter range fighters (Spitfires, P-47s and Typhoons) could now reach Luftwaffe fighter bases.

My regards,

Widewing

[Crumpp]

The Germans or Focke Wulf never abanoded race for high altitude performance, they were just unable to field their high altitude piston engine developements; the Ta 152H was too little too late, most other piston engined high altitude developements were failures.

Bureaucratic infighting caused their engine developments to be failures.  NOT through a lack of materials technology availability.  The beliefs the Germans could not develop adequate supercharger technology or lacked high strength alloys are a myth.

Crumpp

[Crumpp]

It's unbelieveable too that the decision was made to regulate the P51B's to a tactical role.  Of all the allied fighters in service at the time the P51B was the best suited for dogfighting the FW-190A.

The Spitfire Mk IX was the performance equal of the FW-190A.  It held some advantages but the FW-190 had some cards too.  Each of the planes strength canceled the others weakness and pilot skill was left to decide the outcome.

The P51B had advantages in level speed, dive, and a "slight' turn advantage.  Only in roll rate and climb did the FW-190 hold any cards.

The level speed advantage was commanding.  50 mph rising to 70 mph at some altitudes.  This translated to a better zoom climb if the P51 was at speed also.

Crumpp