Author Topic: Captured German La-5 flight test (Read 8917 times)

HoHun · « **Reply #60 on:** October 27, 2003, 05:39:33 PM »

Hi everyone,

here's more information about captured Lavochkins:

http://pub157.ezboard.com/fluftwaffeexperten71774frm62.showMessage?topicID=2.topic

Regards,

Henning (HoHun)

dtango · « **Reply #61 on:** October 28, 2003, 04:25:39 PM »

Hi guys: great discussion going on here!

I've been away for quite awhile with the arrival of a new 2 month old and thought I would pop my head in here to see what was going on. Between him and his brother they've evened the odds out at our household 1 to 1 between parents and kids! This is my first opportunity to think about things aerodynamic in a long time hehe.

Nice to see some good flight performance and specific aircraft technical discussions going on here! Very intelligent posts by all involved starting with F4UDOA on down.

I think HoHun does a nice summation of the analysis of the data.

Quote

The conclusion to draw from this is that Lerche's test aircraft had a significantly higher coefficient of drag than the Tsagi test aircraft.

The cowling theory HoHun brings up is really interesting in contributing to drag of the aircraft. Another similar factor that could be at play as well is the condition of the aircraft itself. Quoting from the original doc posted by F4U...

Quote

The aircraft itself was fully serviceable. Its flying hours are not known bu the machine has been in service for some time. Surface finish, especially that of the wings (wood) is good;

Joeblogs and Tilt's comments touch on this a bit regarding production model VVS aircraft. Multiply that by the "machine being in service for some time"- e.g. fairings no longer sealed well, cowling issues etc. could result in the drag differential we're seeing at max level speeds? Something to think about.

Also do we know if compressibility correction is applied to the Tsagi max speed data?

I'm also puzzled by the WEP comment in the document. Joeblogs and Tilt postulated on the effect of ram air cooling (or lack there of) impacting the inability to reach WEP ratings. What strikes as even odder is the statement about not being able to attain WEP in horizontal flight as well.

I agree with HoHun's statement...

Quote

Whether this problem was specific to Lerche's test aircraft, or whether it was common - or even typical - for Lavochkins in VVS service can't be determined from Lerche's report, though.

Tango, XO
412th FS Braunco Mustangs

HoHun · « **Reply #62 on:** October 31, 2003, 07:13:52 PM »

Hi everyone,

>The 8-... designation is an RLM habit - every aircraft (and engine, and propeller ...) seems to have had an 8- designation for some reason. This doesn't give away the version, though.

After having read Edwin Black's "IBM and the Holocaust", I'd say it could be that the "8" of the RLM designation was some punch card code for aviation hardware.

I'd speculate that the RLM also administered stuff with different codes, like "1" for uniforms, "2" for ground vehicles etc.

Regards,

Henning (HoHun)

MiloMorai · « **Reply #63 on:** December 15, 2003, 07:34:44 AM »

Quote

Originally posted by HoHun
Hi everyone,

>The 8-... designation is an RLM habit - every aircraft (and engine, and propeller ...) seems to have had an 8- designation for some reason. This doesn't give away the version, though.

After having read Edwin Black's "IBM and the Holocaust", I'd say it could be that the "8" of the RLM designation was some punch card code for aviation hardware.

I'd speculate that the RLM also administered stuff with different codes, like "1" for uniforms, "2" for ground vehicles etc.

Regards,

Henning (HoHun)

The RLM prefix code for re-action propulsion engines was 109, was it not? This was sometimes shortened to just a 9 it seems.

Do any know what all the prefix codes used by the RLM are?

HoHun · « **Reply #64 on:** July 13, 2004, 11:47:03 PM »

Hi Tilt,

>The statement re WEP again (for me) confuses the use of WEP in the La 5FN (V). I have other documents that infer that its WEP was not of the duration that could be used on the La7 (Albeit for earlier La5FN models.) And only safely used for 2 mins.

>However this quotes the manifold pressure at 2500rpm at 1180......I thought it was higher than this at 2500rpm (1200 ). Indeed at 2600 rpm the pilots notes claim that manifold should be 1260 but his could only be used at take of for no more than 30 secs!

There's a German performance curve for the M-82FNV that shows 2500 rpm, 1.63 ata = 1199 mm Hg yielding 1850 HP at sea level (could be 1.68 ata = 1235 mm Hg). It's labeled "Start" (take-off) and only to be used to up to of 300 m (I suspect that's without ram effect), which looks like close to the full throttle height for that setting.

There's also a M-82 curve on the same page, which seems to indicate that the M-82 had the same supercharger gearing for the high gear at least. The data on another page confirms that the gearing is the same for both gears, actually. Still, the Tsagi climb graphs for the La-5FN seem to indicate that the graphed performance was reached with an engine with lower high gear supercharger ratio, which I assume was the M-82FN.

>One was an Article by Alexyenko and Kondratiev that had been translated. I do not know the credentials of either.

>Another were a couple of Czech articles.

>In an out of print book called "In the cockpit" there is an article written consulting two Czech pilots who flew La5FN's.

>They refer to 2500 rpm "take off power" that could only be used for 2 minutes.......

Very interesting. Note that Lerche states that full emergency power cannot be reached in the capture La-5FNV as the engine doesn't develop full boost. Maybe that's part of the explanation why it didn't perform correctly - I'll have to revisit the climb performance to check the power again.

>We then look at the development criteria for the La7 and we see the cowling was subject to considerable work. Not only for external steam lining but also with respect to internal air flow.

Squadron/Signal "La-5/La-7 fighters in Action" mentions that the relocated oil cooler on the La-5 "206" (similar to La-7 position) improved air flow through the cooler by 35%.

By the way, do you know the propeller diameters for the La-5FN respectively the La-7? I haven't found these yet.

Regards,

Henning (HoHun)

Crumpp · « **Reply #65 on:** July 14, 2004, 08:27:05 AM »

Quote

There was a 50kg weight imbalance that still intrigues me.

I am by no means an expert on VVS A/C. I was doing some research on the FW-190 and came across some interesting features which could explain the 50Kg balance.

Many WWII A/C placed the Oxygen tanks in the wing. If the VVS used a high pressure tank (compressed O2), continuos flow regulator system then that would explain the weight. This was the most common Oxygen system for the Allies until late in the war.

The Germans did not use compressed O2 in their oxygen delivery systems. They used Liquid Oxygen in small high pressure spherical cylinders. Very similar to a "Power Tank" if any of you go 4 wheeling.

The compressed O2 high pressure tanks would have been larger and heavier. 50 Kg is probably about right to balance it out 3-4 steel High Pressure gas cylinders.

Crumpp

HoHun · « **Reply #66 on:** July 15, 2004, 12:45:46 AM »

Hi Tilt,

>Note that Lerche states that full emergency power cannot be reached in the captured La-5FNV as the engine doesn't develop full boost

I should have added "in high superharger gear" here.

>I'll have to revisit the climb performance to check the power again.

From a quick comparison of the Tsagi La-5FN (1943) data, it seems like they used full emergency power for the speed graph, but some 100 HP less for the than that for the climb graph. Of course, that La-5FN (1943) probably was powered by an Ash-82FN (not the FNV I'm using for comparison with the captured La-5FNV), and unfortunately I don't have a power curve for the Ash-82FN.

Regards,

Henning (HoHun)

VooDoo · « **Reply #67 on:** July 15, 2004, 01:11:11 AM »

Normal WEP for La-5FN, La-7 was 2500 rpm, 1180 mm hg. Its manual and test data.

I should have added "in high superharger gear" here.
This is not a bug - this is feature

.

"Then using supercharger second speed - do not allow manifold pressure higher than 1000 mm hg to avoid detonation..."

Its from La-5FN manual.

Tilt · « **Reply #68 on:** July 15, 2004, 05:02:11 AM »

Voodoo (I think) is correct.

Pre detonation is a function of overheating..so inadequate head cooling would have limited the use of higher powers......particularly during climb.............infact at level speeds over cooling was also a problem.

2500 rpm was only used to augment power in the lower supercharger gear...........infact the higher gear did not bring any benefit (or could not be used for other reasons) below circa 14,000 ft ( this would vary by a few hundred feet as to whether the ac was in climb or level at speed [ram effect again])

The oxygen bottle is central in the fuselage it was there for the pilot to breath. Compressed air tank was also centrally stored.

The only out of balance systems were the pitot and the flap actuating cylinder which would have acounted for no more than a few kgs.

The most likely out of balance force would have been an uneven fuel load. Wing tanks drained through non return valves to the central fuselage tank............. I can see no governing system to ensure they both drain evenly (although there is a fuel valve on the cockpit floor of unknown functionality). Hence G forces could have effected the balance of drain............but 50kgs still seems a lot even for this phenomenom.

I too struggle to find the diameter of the la5 prop (same as Lagg3)......I know the La7 prop. I know its longer than the la5 prop I know the gear is 120mm longer on the La7 to compensate for the longer prop.

The only dif between the FNV and the FN (that I know of) was the 2nd stage super charger speed. (other than the later addition of a true MP/RPM governor)

The oil cooler design was more efficient and so could be (and was) made smaller. The poor pilot on the other hand was troubled with "hot feet" by the hot oil pipes bolted directly under the cockpit floor.

Its the improve ment in the engine cowling and exhaust system that allowed cooling air to be better distributed across all (and in particular the upper) cylinders that (I believe) would acount for longer use of WEP on the La7.

Voodoo do you have access to an La5FN manual?

gripen · « **Reply #69 on:** July 15, 2004, 05:20:10 AM »

The higher speed of the SC at hi-gear at given altitude and air temperature causes warmer charge and throttling of the engine (to keep MAP down) heats charge even more => detonation at lower MAP than the SC at lo-gear.

gripen

VooDoo · « **Reply #70 on:** July 15, 2004, 05:27:26 AM »

http://www.airwar.ru/other/bibl/la5fn.zip

Tilt · « **Reply #71 on:** July 15, 2004, 06:02:10 AM »

Quote

Originally posted by VooDoo
http://www.airwar.ru/other/bibl/la5fn.zip

Superb!........I can see endless hours with my Russian dictionary ahead

Thank you very much

VooDoo · « **Reply #72 on:** July 15, 2004, 08:45:23 AM »

I hope that you'll notice all other stuff

http://www.airwar.ru/other/bibl/il2rle.zip
http://www.airwar.ru/other/bibl/la5manual.zip
http://www.airwar.ru/other/bibl/lagg3rle.zip
http://www.airwar.ru/other/bibl/tu2man.zip
http://www.airwar.ru/other/bibl/yak3.zip

Crumpp · « **Reply #73 on:** July 15, 2004, 09:01:50 AM »

Quote

The oxygen bottle is central in the fuselage it was there for the pilot to breath. Compressed air tank was also centrally stored.

Are you sure about this? The Germans used both fuselage and wing Oxygen storage not only depending on the TYPE of fighter but also the Sub-varient. So it is possible to find with the Bf-109 series, sub-varients which mounted wing O2 storage tanks and other which had fuselage tanks.

Maybe the VVS did the same. Do you know what type of O2 system they used.

There are so many unknown factors about VVS A/C that it is hard to seperate the fact from the fiction.

Thanks Tilt!
Great thread BTW. I'm learning quite a bit about the La series!

Crumpp

Tilt · « **Reply #74 on:** July 15, 2004, 09:59:18 AM »

Quote

Originally posted by VooDoo
I hope that you'll notice all other stuff

http://www.airwar.ru/other/bibl/tu2man.zip

Do you know the location of a cockpit layout for the Tu2?