buffnut453
Captain
Expert
/ˈekˌspərt/
noun
Person from out of town with a brief case
Ex-spurt....Ex as in has-been, spurt as in drip under pressure
Groundhog Thread Part Deux - P-39 Fantasy and Fetish - The Never Ending Story (Mods take no responsibility for head against wall injuries sustained)
- Thread starter greybeard
- Start date
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Ex-spurt....Ex as in has-been, spurt as in drip under pressure
buffnut453
Captain
So we have the lightweight, non-combat capable P-39C that, in early 1941, can reach 30,000ft in 18.4 mins and has an absolute ceiling of 34,150ft.
For comparison, here's a Spitfire MkI trial from 19 March 1940 showing performance with a constant speed Rotol propellor (source: Spitfire Mk I Performance Testing)
Service ceiling = 34,700 ft.
And we're supposed to believe that taking some guns and 100lb out of the P-400 or P-39D is going to "improve performance tremendously" when the lightweight P-39C was bested by an aircraft that was operational a year before it?
And, just for grins, here's the same table for the Spit MkII (Source: Spitfire Mk IIA Performance Testing):
Service Ceiling: 37,000ft
The MkII entered service in June 1940 and was considered operational in August of that year.
For comparison, here's a Spitfire MkI trial from 19 March 1940 showing performance with a constant speed Rotol propellor (source: Spitfire Mk I Performance Testing)
Height ft. | T.A.S. m.p.h. | Time From Start Min. | Rate of Climb Ft./Min. |
2,000 | | .7 | 2,820 |
5,000 | | 1.8 | 2,850 |
10,000 | 320 | 3.5 | 2,895 |
11,000 | | 3.9 | 2,905 |
15,000 | 339 | 5.4 | 2,430 |
18,900 | 354 | | |
20,000 | 353.5 | 7.7 | 1,840 |
25,000 | 345 | 11.0 | 1,250 |
30,000 | 319 | 16.4 | 660 |
Service ceiling = 34,700 ft.
And we're supposed to believe that taking some guns and 100lb out of the P-400 or P-39D is going to "improve performance tremendously" when the lightweight P-39C was bested by an aircraft that was operational a year before it?
And, just for grins, here's the same table for the Spit MkII (Source: Spitfire Mk IIA Performance Testing):
Height Feet | Top Speed M.P.H. | Time To Climb Mins. | Rate of Climb Ft./Min. |
S.L. | 290 | - | . |
2,000 | 294 | 0.7 | 2925 |
5,000 | 306 | 1.7 | 2955 |
10,000 | 326 | 3.4 | 2995 |
15,000 | 345 | 5.0 | 2770 |
20,000 | 351 | 7.0 | 2175 |
25,000 | 338 | 9.6 | 1600 |
30,000 | 321 | 13.7 | 995 |
The MkII entered service in June 1940 and was considered operational in August of that year.
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I just called it a faked test report and someone got upset. 3 consecutive figures of 3,720 for rate of climb exactly the same mean thrust, lift drag remained almost the same from SL to 10,000ft the difference exactly compensated for the loss of fuel and oil burned. Or it was faked. estimated or averaged out.That's unusual!
The Spitfire I has exactly the same time to climb as that stated for the P-39C to 25,000ft, despite the Spit. being considerably lighter, with more wing span and wing area. It isnt impossible but needs special aerodynamics to produce more lift with less drag.
FLYBOYJ
"THE GREAT GAZOO"
I think you'll find that steel was used in many high stressed areas on several combat aircraft of the period. In later years 7075 forgings or titanium would be used in these applications but you still might find steel depending on the type of aircraft and manufacturer.
The Spitfire always had steel wing spars and was always a light design, the Blenheim used steel box work in its structure and was always a deceptively heavy light bomber. Ingenuity counted for a lot at the time.
GrauGeist
Generalfeldmarschall zur Luftschiff Abteilung
The Me262 used steel skin instead of aluminum due to a shortage of the latter.
P-39 Expert
Non-Expert
This graph is a projection, not actual. Dates on graph predate production. I'm referring to the July 1941 P-39C Wright Field test.
P-39 Expert
Non-Expert
Radio: AHT listed the voice radio in empty weight, IFF radio as part of load. What else would it be?AHT says in the table.
"Misc. equip (radio)"
If it says IFF somewhere else please point it out.
The radio was included in the empty weight of the P-39C as per the Manual.
It was NOT included in the empty weight of the P-39D-1 and P-39D-2 as per the manual.
By the time you get to the P-39N the radios (included is the IFF) are back to being in the empty weight. They are the same radios as used in the P-39Ds. They are listed by type/model number. This probably one of the reasons the P-39N was about 100lbs heavier empty than the P-39D?
Make sure you are comparing like to like.
So you used a WAG to come up with your number.
You could have just used the armament provision number for the P-39D-2
Funny thing about that.
In the Manual for the P-39C the performance number page (page 22) says the level speeds were with a design gross weight of 662lbs. an obvious typo.
The climb data (IAS as various altitudes, no climb rate given) was for a design gross weight of 6662lbs.
The landing and take-off distances are given for a design weight of 6662lbs.
the weight chart comes up with a weight of 6684lbs with 104 gallons of fuel. There are no self sealing tank liners or tanks. full fuel is 170 gallons.
Things change with time. This was common practice in the late 30s or 1940 (?)
The P-36 and early P-40 performance specifications also use a limited fuel load. The performance numbers are done with 105 gallons in the case of the P-36 with a 57 gallon overload tank available
see http://www.wwiiaircraftperformance.org/P-36/P-36_Operation_and_Flight_Instruction.pdf
The P-40 numbers are really strange.
see; http://www.wwiiaircraftperformance.org/P-40/P-40_Official_Summary_of_Characteristics.pdf
normal fuel is 120 gallons, max is 181 gallons.
Performance numbers are for 120 gallons. at a design weight of 6787lbs
So, in this case the P-39C was tested at about 27lbs over it's "design" gross weight. Which is close enough, maybe they couldn't find a test pilot that weighed 160lbs in flight suit and with parachute.
If it is you are going to run out of oil before you run out of gas. P-39N carried 62lbs of oil including the gear box oil for it's 87 gallons of fuel. The P-39Ds carried 88lbs of oil including the gear box oil, Both could and did carry more oil when the drop tank was fitted. The P-39C carried 7.4 gallons in the main tank/engine (55lbs) with 15lbs for the gear box on a separate line. The tank could hold 12.1 gallons. Again the "normal" fuel load for the P-39C was 104 gallons.
Perhaps planes in combat zones carried an extra gallon or two just for "insurance"?
I know I would try to, especially if the engine was somewhat worn.
Apparently the P-39C had semi automatic cooling flaps. At high speed the airflow pushed them shut.
There is also a difference between a plane that has trouble cooling in a long hard climb and one that overheats in high speed level flight.
Yes WAG for 30cal portion of "Armament Provisions". Please provide a more accurate WAG.
Average American man in the Army in WWII was 5'8" and weighed 140lbs. Fast food hadn't been invented yet.
What is your point about the amount of oil?
No auto cooling flaps. Spring loaded, airstream pushed them back partly closed.
Are you saying that the P-400 weights I furnished are not correct?
What is your point about all this? Arguing about the weight of every component, presenting and representing discredited tests. It has been going round and around for years.
Even the name P-400 is a laugh, why not the P-350? You cannot make a case for the P-39 being a good aircraft ever.
33k in the air
Staff Sergeant
- 1,349
- Jan 31, 2021
That the P-39 was the F-22 of its day? Something like that, it seems.
It would have been if gravity and the British hadnt got involved in an unholy conspiracy.
Even the stuff about radios I dont get, the British had been using radios in planes since around 1930, I cant believe the USA was any different because pictures of the Boeing P-26 have aerials on and the Gloster Gladiator had them. At the time a better radio wouldnt be lighter, it would be about the same as others but with more range and channels. I really dont get the point at all. This is a good read into the radio side of aviation warfare SpitfireSpares.com - warbird Instruments
Shortround6
Major General
Where in AHT does it say that?
The manuals for the later P-39s have the radios in the empty weight. But the manual for the D-1 and D-2 definitely have them in the basic load section.
Weight and balance chart may list things differently than a construction specification chart.
P-39K has a
Great, naked pilot with 20lb parachute.
By the P-39K & L manuals the pilot & parachute allowance was 200lbs.
I guess fast food was not only invented but widely distributed on/near AAC bases by the end of 1942?
Point is you have to use the right weight for the mission, not the weight that looks the best.
P-39K & L used 71lbs total but then they are listed as using 104 gallons fuel as normal load with 16 gallons as internal overload.
You may need another 8lbs of oil if you fill the fuel tanks to 120 gallons.
You are the one saying the P-39 could have been used for escort missions, not without more oil and weight.
You may want to find some other aircraft that changed weights by 300-500lbs and see what kind of difference it made.
P-40 Kittyhawk in British test showed a 110fpm loss in climb with the 52 US gallon drop tank fitted. Granted the Kitty hawk was not very good climbing to begin with but a change of 360lbs didn't do much either for or against the plane.
Spitfire V with four 20mm cannon and a nearly 400lb weight gain over a standard Vb lost 350fpm in climb and took an extra 1 minute even (0 seconds) to reach 20,000ft. It was actually 3mph faster.
Couldn't ball turret gunners be re trained to fly P-39s? I am trying to think outside the box.
Thumpalumpacus
Major
Radios? Who needs radios?
IFF? Who needs that?
Guns? Who needs more than three?
Range? I've got a range in my kitchen, dammit. I don't need another range.
Gotta like
P-39 Expert
, he'll break out a Ditchwitch digging a hole in defense of his favorite airplane. Shame he can't really put things into perspective, but hey, there's a lot like him: far too invested emotionally to think rationally at all.
It's only a matter of time before he figures out how to hang a Genie on a 'Cobra and be shooting down Tu-95s well into the 60s.
IFF? Who needs that?
Guns? Who needs more than three?
Range? I've got a range in my kitchen, dammit. I don't need another range.
Gotta like
P-39 Expert
, he'll break out a Ditchwitch digging a hole in defense of his favorite airplane. Shame he can't really put things into perspective, but hey, there's a lot like him: far too invested emotionally to think rationally at all.It's only a matter of time before he figures out how to hang a Genie on a 'Cobra and be shooting down Tu-95s well into the 60s.
buffnut453
Captain
Actually since 1918. There was operational use of radios for air-to-ground communication in 1918 by 11 Sqn RAF.
I didnt know when they switched from Morse to voice.
Shortround6
Major General
They tried carrier pigeons but they kept getting hit by the tail surfaces when released.
My coat is nearby.
My coat is nearby.
You jest? Bomber command aircraft carried pigeons throughout most of the war (until 1943) Carrier Pigeons in the Bomber War
