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Questions on the P-39L-1

istari6

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istari6

istari6

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One of the things I love about IL-2 is how it triggers curiosity to learn more about each aircraft.  I knew little about the P-39 beyond it's reputation in the Pacific as the "Iron Dog".  However,  after reading a number of forum threads and researching further online, there's still questions I'm hoping to pin down:

 

1. What is that loud distinctive whine?   [Answered.  Thanks]
 
I know the P-39 had an unusually long transmission shaft forward from the mid-fuselage engine, but the reduction gear at the propeller should be the same as any other aircraft.  Is there something else causing this strange whine from the front quarter?
 
2. What is the window for in the left forward canopy? 
 
Never seen this on any other aircraft.  Ventilation?   [Answered.  Thanks]
 
3. Why is the P-39 so heavy?  (given small size)
 
Having heard it was the smallest US fighter, with a 35' wingspan to 37' for P-40 and P-51, I was surprised to see in-game that P-39L-1 is 6457 lb empty compared to 6774 lb for the P-40E-1.  It looks significantly smaller than the P-40 on the ground.  Is this the M4 cannon and ammunition?  Just a much more tightly packed airframe compared to the Warhawk?
 
4. How sturdy was the landing gear on P-38, P-39?  Why wasn’t tricycle gear used for P-47/P-51?   [Answered.  Thanks]
 
I'm really impressed at how much the tricycle gear makes taxiing, takeoff and landing much easier in the Airacobra.  Feels like a Cessna 172.  Yet the fighters that followed (P-47, P-51) didn't use the tricycle gear design.  Why?  
 
5. Why wasn’t the rear mounted engine used afterwards?  Sensitivity to quick engine power changes?  Breakage risk from extended crankshaft?  
 
Even if you don't mount a 37mm cannon, the advantage of nose-mounted weapons is significant (see the P-38 Lightning).  Why didn't other aircraft manufacturers copy the Airacobra design to allow central mounting of armament? 
 
6. Was the radio really that superior for the Soviets in 1943?  [Answered.  Thanks]
 
It seems that on the P-39s biggest advantages for the VVS in the Battle of the Kuban was the radios.  I know that in 1941, many Soviet fighters lacked radios entirely.  But by 1943, didn't the Soviets have basic transmit/receive radios on all fighters being produced?  What made the P-39s radios so different and game-changing?  
 
Thanks for any answers to the above!  

 

Sources I reviewed before writing this post (in case this helps others find info faster):

 

Edited by istari6
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LukeFF

LukeFF

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Posted (edited)
4 hours ago, istari6 said:
6. Was the radio really that superior for the Soviets in 1943?
 
It seems that on the P-39s biggest advantages for the VVS in the Battle of the Kuban was the radios.  I know that in 1941, many Soviet fighters lacked radios entirely.  But by 1943, didn't the Soviets have basic transmit/receive radios on all fighters being produced?  What made the P-39s radios so different and game-changing?  

 

Even by 1943, the quality of the radios being built in the US was far superior to anything being built by the Soviets - even if they were being installed as full sets in fighter aircraft by then. Poor shielding seems to be the primary cause of that. Unless a regiment had someone that could work miracles and fix the problem, the radios were going to be a liability. The book Red Star Against the Swastika is full of accounts from the author's regiment about poor radio reliability - even by 1943.

Edited by LukeFF
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cardboard_killer

cardboard_killer

Posted
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4 hours ago, istari6 said:

Why wasn’t tricycle gear used for P-47/P-51?  

 

Space for forward gear was taken up by the engine. The P-39 and P-38 did not have that problem.

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istari6

istari6

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2 hours ago, cardboard_killer said:

Space for forward gear was taken up by the engine. The P-39 and P-38 did not have that problem.

 

Ah... Of course (smacks forehead).  Tricycle gear wasn't really possible for single-engine fighters until rear-mounted engines became standard with jet aircraft. 

Edited by istari6
twilson37

twilson37

Posted
Posted

How sturdy was the landing gear on P-38, P-39?

I remember hearing that some of the pilots on Guadalcanal had their front nose gear collapse and often this led to the engine coming loose from its mounts and ending up in the cockpit.

Why wasn’t the rear mounted engine used afterwards?  Sensitivity to quick engine power changes?  Breakage risk from extended crankshaft?  

I  think the center mounted engine created an issue in a stall, with less weight in the nose the plane had a tendency to spin and not get its nose pointed downwards. Also with the engine in the rear you had to come up with a more sophisticated routing of flight control cables to the tail.  I also think the sub-par performance of the large gun made such trade-off unnecessary

istari6

istari6

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4 hours ago, LukeFF said:

Even by 1943, the quality of the radios being built in the US was far superior to anything being built by the Soviets - even if they were being installed as full sets in fighter aircraft by then. Poor shielding seems to be the primary cause of that. Unless a regiment had someone that could work miracles and fix the problem, the radios were going to be a liability. The book Red Star Against the Swastika is full of accounts from the author's regiment about poor radio reliability - even by 1943.

 

How did poor shielding affect Soviet radios?  Did it cause them to fail, or was it just limited power/range/intelligibility?  Just trying to understand what the US radios were doing so much better than enabled VVS Airacobra pilots to make a breakthrough in tactics.   

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LukeFF

LukeFF

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3 hours ago, istari6 said:

How did poor shielding affect Soviet radios?  Did it cause them to fail, or was it just limited power/range/intelligibility?  Just trying to understand what the US radios were doing so much better than enabled VVS Airacobra pilots to make a breakthrough in tactics.   

 

I think the big issue was audio clarity - all the background noise with the engine running interfered with the ability to hear messages clearly. That same sort of thing still happens, for instance, with headphones that have poor shielding - you get all sorts of background noise interference. 

 

In that book I mentioned up above, there's a few instances of pilots being berated once back on the ground for not responding to radio messages. The problem? The pilots said they simply never heard the message come through. 

ZachariasX

ZachariasX

Posted
Posted
3 hours ago, istari6 said:

How did poor shielding affect Soviet radios? 

You also need electrical shielding. If that is not done perfectly, you‘ll hear the ignition system in your radio that considerably degenerates audio clarity. It is not that sraight forward to isolate this high voltage system from something as sensible as a radio circuit.

 

Basically none of todays FM radios really work anymore in vintage cars. You get terrible static noise (you hear the ignition sparking) as today, cars are built such that the high voltage part is well shielded from the rest and you do not require such shielding in the radio. But old Delco FM radios for instance filter that very well and perform FAR better than anything you can buy on AliExpress.

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6./ZG26_5tuka

6./ZG26_5tuka

Posted
Posted
12 hours ago, istari6 said:

1. What is that loud distinctive whine?  

 
I know the P-39 had an unusually long transmission shaft forward from the mid-fuselage engine, but the reduction gear at the propeller should be the same as any other aircraft.  Is there something else causing this strange whine from the front quarter?

It apparently originates from the drive shaft probably due to bearing causing a lot of mechanical noise inside. Here's some footage from the real one.

 

 

 

 

 

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MattS

MattS

Posted
Posted
18 hours ago, istari6 said:

One of the things I love about IL-2 is how it triggers curiosity to learn more about each aircraft.  I knew little about the P-39 beyond it's reputation in the Pacific as the "Iron Dog".  However,  after reading a number of forum threads and researching further online, there's still questions I'm hoping to pin down:

 

1. What is that loud distinctive whine?  
 
I know the P-39 had an unusually long transmission shaft forward from the mid-fuselage engine, but the reduction gear at the propeller should be the same as any other aircraft.  Is there something else causing this strange whine from the front quarter?
 
2. What is the window for in the left forward canopy? 
 
Never seen this on any other aircraft.  Ventilation? 
 
3. Why is the P-39 so heavy?  (given small size)
 
Having heard it was the smallest US fighter, with a 35' wingspan to 37' for P-40 and P-51, I was surprised to see in-game that P-39L-1 is 6457 lb empty compared to 6774 lb for the P-40E-1.  It looks significantly smaller than the P-40 on the ground.  Is this the M4 cannon and ammunition?  Just a much more tightly packed airframe compared to the Warhawk?
 
4. How sturdy was the landing gear on P-38, P-39?  Why wasn’t tricycle gear used for P-47/P-51?  
 
I'm really impressed at how much the tricycle gear makes taxiing, takeoff and landing much easier in the Airacobra.  Feels like a Cessna 172.  Yet the fighters that followed (P-47, P-51) didn't use the tricycle gear design.  Why?  
 
[Why wasn't tricycle gear used for P-47/P-51 - answered.  Thanks]
 
5. Why wasn’t the rear mounted engine used afterwards?  Sensitivity to quick engine power changes?  Breakage risk from extended crankshaft?  
 
Even if you don't mount a 37mm cannon, the advantage of nose-mounted weapons is significant (see the P-38 Lightning).  Why didn't other aircraft manufacturers copy the Airacobra design to allow central mounting of armament? 
 
6. Was the radio really that superior for the Soviets in 1943?
 
It seems that on the P-39s biggest advantages for the VVS in the Battle of the Kuban was the radios.  I know that in 1941, many Soviet fighters lacked radios entirely.  But by 1943, didn't the Soviets have basic transmit/receive radios on all fighters being produced?  What made the P-39s radios so different and game-changing?  
 
Thanks for any answers to the above!  

 

Sources I reviewed before writing this post (in case this helps others find info faster):

 

 

I don't have answers, but I do want to say that these are high-quality questions!

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Lusekofte

Lusekofte

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10 hours ago, istari6 said:

 

Ah... Of course (smacks forehead).  Tricycle gear wasn't really possible for single-engine fighters until rear-mounted engines became standard with jet aircraft. 

More like high performance aircraft with huge propellers and retractable gear. 
Gull winged Stukas and corsair did not need full length on Their gear to get prop clerance

69th_chuter

69th_chuter

Posted
Posted

Regarding the nose gear, besides space being an issue conventional (then - haha) was both lighter and considered the norm.  The reason tri-gear was introduced was to make life easier for mass produced pilots ... maybe reducing accidents.  None of the nosewheels in game are steerable* so most have shimmy dampeners (the P-39 could sometimes - and the B-24 moreoften) because the shimmy would usually fold up the nosegear.  An interesting "feature" of the nosegear was, typically, once it was flopped all the way over to one side it could be difficult to center as it would flop all the way over to the other side when trying to straighten.  It would sometimes take some power and heavy brake use to get the plane taxing straight -- a kinder crew chief would use the towbar to straighten it for you first - lol.

 

 

*I believe it was the DC-4, C-54, R5D that introduced nosewheel steering in WW2.

 

Avimimus

Avimimus

Posted
Posted
On 5/24/2020 at 2:16 PM, istari6 said:

5. Why wasn’t the rear mounted engine used afterwards?  Sensitivity to quick engine power changes?  Breakage risk from extended crankshaft?  

 

The P-63 is of note (previously mentioned). However, the Belyayev OI-2 and some other Soviet projects used the layout, suggesting that Soviet experience with the P-39 didn't produce an aversion to such layouts, but actually stimulated interest in them - at least to some extent.

 

I'd have been afraid of the crankshaft if I was managing development risk (just from all of the stories I've read about other projects), but it doesn't seem to have been an issue - except possibly where weight is a concern. The common opinion is that the distribution of masses made high angle-of-attack maneuvers and stalls more dangerous. Musing theoretically, it could be possible to shift the CG forward through adding a heavier armament to the front (although this would reduce the view and reduce performance considerably)

 

A predecessor to the P-39, the Bell model 3, had the cockpit moved back to the tail... this allowed a central engine layout and would have solved the center of gravity issues and saved weight. However, the pilot would have much worse visibility and would have been less well protected.

 

P.S.

The Tucker XP-57 was like a miniature P-39... kindof interesting as a point of comparison.

istari6

istari6

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On 5/24/2020 at 10:55 PM, LukeFF said:

think the big issue was audio clarity - all the background noise with the engine running interfered with the ability to hear messages clearly. That same sort of thing still happens, for instance, with headphones that have poor shielding - you get all sorts of background noise interference. 

 

In that book I mentioned up above, there's a few instances of pilots being berated once back on the ground for not responding to radio messages. The problem? The pilots said they simply never heard the message come through.

 

Ah, that makes sense.  So clear and reliable comms on US-built radios allows VVS pilots to develop tactics they can count on using consistently, without depending on the variations of individual radios and their local maintainers.

 

On 5/24/2020 at 7:19 PM, twilson37 said:

How sturdy was the landing gear on P-38, P-39?

I remember hearing that some of the pilots on Guadalcanal had their front nose gear collapse and often this led to the engine coming loose from its mounts and ending up in the cockpit.

 

In "Fire in the Sky", the author talks about the early US P-39 pilots being very nervous about the rear-mounted engine for the reasons you mention.  Would it break loose and crush them in a mishap?  Yet apparently it wasn't an issue at all in practice.  The Allison was mounted very securely into the airframe, no greater risk to pilot than other types.  

 

The weakness of the nose-mounted strut is confirmed by early experience in the South Pacific on rutted, poor condition airfields.  One of the enhancements in the P-39L-1 was a "stiffened nosewheel fork", don't know how successful it was in reducing strut collapse.    

 

On 5/24/2020 at 11:09 PM, ZachariasX said:

You also need electrical shielding. If that is not done perfectly, you‘ll hear the ignition system in your radio that considerably degenerates audio clarity. It is not that sraight forward to isolate this high voltage system from something as sensible as a radio circuit.

 

Basically none of todays FM radios really work anymore in vintage cars. You get terrible static noise (you hear the ignition sparking) as today, cars are built such that the high voltage part is well shielded from the rest and you do not require such shielding in the radio. But old Delco FM radios for instance filter that very well and perform FAR better than anything you can buy on AliExpress.

 

Electrical shielding seems something much more responsive to US manufacturing than noise shielding.  Hard to believe the P-39 cockpit was that much quieter or Soviet headphones were so poorly padded if that made a life-or-death difference for radio communications.  But radio units with effective electrical shielding might be hard to mass-produce from relatively unskilled labor in the Urals.  

 

On 5/24/2020 at 11:43 PM, 6./ZG26_5tuka said:

It apparently originates from the drive shaft probably due to bearing causing a lot of mechanical noise inside. Here's some footage from the real one.

 

Yeah, that second video really brings out the whine we hear in game.  My old physics training taught that sound is energy being wasted.  I could imagine a damaged gearbox or one without oil (soon to be damaged :>) making this noise, but surprised that a well-oiled and properly functioning gearbox is so noisy. 

 

19 hours ago, chuter said:

Regarding the nose gear, besides space being an issue conventional (then - haha) was both lighter and considered the norm.  The reason tri-gear was introduced was to make life easier for mass produced pilots ... maybe reducing accidents.  None of the nosewheels in game are steerable* so most have shimmy dampeners (the P-39 could sometimes - and the B-24 moreoften) because the shimmy would usually fold up the nosegear.  An interesting "feature" of the nosegear was, typically, once it was flopped all the way over to one side it could be difficult to center as it would flop all the way over to the other side when trying to straighten.  It would sometimes take some power and heavy brake use to get the plane taxing straight -- a kinder crew chief would use the towbar to straighten it for you first - lol.

 

Never thought about the fact that a nosewheel strut costs more weight (including retraction gears, hydraulics, etc) than a simple tailwheel.  

 

 

7 hours ago, Avimimus said:

The P-63 is of note (previously mentioned). However, the Belyayev OI-2 and some other Soviet projects used the layout, suggesting that Soviet experience with the P-39 didn't produce an aversion to such layouts, but actually stimulated interest in them - at least to some extent.

 

I'd have been afraid of the crankshaft if I was managing development risk (just from all of the stories I've read about other projects), but it doesn't seem to have been an issue - except possibly where weight is a concern. The common opinion is that the distribution of masses made high angle-of-attack maneuvers and stalls more dangerous. Musing theoretically, it could be possible to shift the CG forward through adding a heavier armament to the front (although this would reduce the view and reduce performance considerably)

 

Now that I'm reading about the new Yak-9T, I wonder how much that was inspired by the Soviet's positive experience with the P-39?  As for the reliability of the crankshaft, my impression is that there is a higher risk of engine failure with sudden throttle inputs in the P-39.  I think this is historical because of the torque effects being transmitted down this long crankshaft.  

 

On 5/25/2020 at 5:21 AM, MattS said:

I don't have answers, but I do want to say that these are high-quality questions!

 

Thanks!

Edited by istari6
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TheSublimeGoose

TheSublimeGoose

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On 5/24/2020 at 6:19 PM, LukeFF said:

 

Even by 1943, the quality of the radios being built in the US was far superior to anything being built by the Soviets - even if they were being installed as full sets in fighter aircraft by then. Poor shielding seems to be the primary cause of that. Unless a regiment had someone that could work miracles and fix the problem, the radios were going to be a liability. The book Red Star Against the Swastika is full of accounts from the author's regiment about poor radio reliability - even by 1943.


The very first combat operation flown by P-47s in Europe -- in mid-1943, I believe -- was cut short because of the poor quality (or simply performance) of the US radios. They didn't fly again for 2 weeks, after having British radios installed.- source

No word on why these 'malfunctions' occurred, so I suppose it doesn't necessarily speak to the quality of the radios. Could have been external factors, I suppose... or just those specific radios that had issues.

1 hour ago, istari6 said:

 

Now that I'm reading about the new Yak-9T, I wonder how much that was inspired by the Soviet's positive experience with the P-39?  As for the reliability of the crankshaft, my impression is that there is a higher risk of engine failure with sudden throttle inputs in the P-39.  I think this is historical because of the torque effects being transmitted down this long crankshaft.  


Very good point, never thought of that. I'd like to know folk's thoughts on this, as well.

Additionally, to add another question to OP's list:

The P-400 and a few other P-39 models were armed with the AN/M2 20mm in the nose vice the standard 37mm trebuchet. I'm surprised the 20mm wasn't more popular, as I'd imagine it would greatly improve one's fighting ability against fighters. As the 39 was (sort of) sold as an interceptor originally, it was designed around the large 37mm, obviously envisioned as a sort of short-range, low-medium altitude bomber-destroyer, complemented by the longer-range, high-altitude P-38. But again, in the hands of the Soviets, I would've thought that the 20mm would be preferred when scrapping with Luft fighters. Higher velocity, higher RoF, and a higher ammunition count... whereas the 37 must've been a pain to hit fighters with. Did operational Soviet units ever swap the 37 out for the 20? Was there any any serious consideration of scrapping the 37 in place of the 20?

Avimimus

Avimimus

Posted
Posted
1 hour ago, istari6 said:

Now that I'm reading about the new Yak-9T, I wonder how much that was inspired by the Soviet's positive experience with the P-39?

 

The NS-37 started development in 1941... and even in the mid-1930s (or back in 1917 with the Spad S.XII ) it was realised that the only way for a small fighter to carry a large cannon comfortably was by firing through the spinner... so it seems somewhat inevitable. However, the success of P-39 pilots might have encouraged the decision to build so many Yak-9T?

BlitzPig_EL

BlitzPig_EL

Posted
Posted

The crankshaft in the P39 was no longer than any other Allison engined aircraft.  The long bit was a driveshaft that connected the engine's crankshaft to the propeller reduction gearbox at the front of the aircraft.  This allowed the aircraft to mount the 37mm gun through the prop hub.

ZachariasX

ZachariasX

Posted
Posted
8 hours ago, istari6 said:

Electrical shielding seems something much more responsive to US manufacturing than noise shielding. 

I doubt that. It's simple to add electrical shielding, but you have to design that and spend electrical parts to make it happen. The Chinese stuff is made as good as a Delco from 1960. I mean, anyone doing semicionductors had to be braindead for not being able to put together an FM radio.  But when you open them up, you see you can make like 100 Chinese radios from one Delco in terms of material put in there. Lately, I had one Delco restored. Basically exchanged all capacitors, resistors, etc. that didn't live up to specs anymore (plenty of those!) after solderning out all of them from the board. Then putting everything back in. Radios made today are not made to tolerate such high voltage noise in their power circuit. You have to specifically add filters. As for the rest, soldering is soldering. No problemo.

istari6

istari6

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Posted (edited)
On 5/26/2020 at 5:10 PM, KotwicaGoose said:

As the 39 was (sort of) sold as an interceptor originally, it was designed around the large 37mm, obviously envisioned as a sort of short-range, low-medium altitude bomber-destroyer, complemented by the longer-range, high-altitude P-38.

 

Huh.  Never thought about the relationship between P-38 and P-39 that way, but it makes sense.  Much like the Bf 109 and Bf 110, although given the Luftwaffe's aggressive doctrine, I think it was always assumed the Bf 110 would be an escort fighter supporting long-range offensive operations.  

 

On 5/26/2020 at 6:23 PM, BlitzPig_EL said:

The crankshaft in the P39 was no longer than any other Allison engined aircraft.  The long bit was a driveshaft that connected the engine's crankshaft to the propeller reduction gearbox at the front of the aircraft.  This allowed the aircraft to mount the 37mm gun through the prop hub.

 

So it was the connection between the crankshaft and the driveshaft that was so noisy?  

 

On 5/27/2020 at 12:18 AM, ZachariasX said:

I doubt that. It's simple to add electrical shielding, but you have to design that and spend electrical parts to make it happen. The Chinese stuff is made as good as a Delco from 1960. I mean, anyone doing semicionductors had to be braindead for not being able to put together an FM radio.  But when you open them up, you see you can make like 100 Chinese radios from one Delco in terms of material put in there.

 

So if I'm following, it's not complex or sophisticated manufacturing.  It's just more costly in basic electrical parts.  The Soviets didn't put a priority on this (despite life-and-death consequences for VVS pilots), while US radio had these additional parts.  I guess I'm just surprised that two years into the war, where the importance of radio communications has now been vividly demonstrated in every aspect of warfare (land, air, sea), the Soviets hadn't added this basic shielding to their radios.  I'd assumed it had something to do with much more sophisticated American manufacturing capabilities.  

Edited by istari6
TheSublimeGoose

TheSublimeGoose

Posted
Posted
1 hour ago, istari6 said:

 

Huh.  Never thought about the relationship between P-38 and P-39 that way, but it makes sense.  Much like the Bf 109 and Bf 110, although given the Luftwaffe's aggressive doctrine, I think it was always assumed the Bf 110 would be an escort fighter supporting long-range offensive operations.  


I'm sure not everyone will agree -- not even all aviation historians seem to agree -- but I truly think this is how the P-38/39 combo was viewed by many within the USAAC. The P-39 was expected to serve a short-range air defense fighter, whereas the P-38 would be the offensive/escort fighter. Much like the 109/110, but as we know, the 38 performed much better than the 110 in the air-superiority role.

Important to note that the XP-39 did indeed mount a turbo-supercharger, giving it decent (although not stellar) high-altitude performance. Bell increasingly had issues with the turbo -- mostly due to limited space -- and eventually the USAAC agreed that it could be axed. The ONLY reason they allowed this to happen, IMO, and didn't cancel the XP-39, was because they knew the P-38 was about to ready. These two fighters were absolutely meant to complement each other, at least in the USAAC's eyes.

Also, another interesting tidbit; The YP-38 was originally intended to mount a 23mm cannon. Then it was switched to a 37mm cannon... the setup didn't work, so they went with the 20mm. Odd that they were able to fit the 37mm in the 39, but not the 38.

FeuerFliegen

FeuerFliegen

Posted
Posted
On 5/28/2020 at 10:42 PM, KotwicaGoose said:

 Odd that they were able to fit the 37mm in the 39, but not the 38.

 

Imagine how nice a P-39 would be with identical armament as a P-38.  Or even minus one or two .50s

Noisemaker

Noisemaker

Posted
Posted

Perhaps a slight aside, but after a cursory google search, I found nothing.  Is there a reason that a fully extendable tail wheel was not explored as a solution to the inherent problems of the tail draggers, rather than a nose wheel?  Obviously it would require a rebalancing of the centre of gravity of the airframe, but is there something that makes the idea unworkable?

69th_chuter

69th_chuter

Posted
Posted

Regarding Item 2, the "Little Window" ...

 

That would be "Ice Window" installed along with the optional glycol de-icing system.  The idea was that if you had to use glycol to remove accumulated ice then you'd probably want to wipe at least part of the windshield off afterword.  A similar window could be found on some P-40E's (not in game), although it's mostly an "N" thing, and on some P-47 Razorbacks (again, not in game).  On the P-40N the window is the extra ~vertical frame (hinge) on the left side aft edge and the Razorback it's similarly the left side aft lower triangular area demarcated by its hinge.  The early Mustang used a wonky squarish window higher up the left side windscreen but not common.  The P-38 never had an ice window because it relied exclusively on hot air anti-icing as did most later aircraft. 

 

The USA didn't feel the need to standardize this de-icing system consequently it's not unusual to find ice windows on aircraft in the tropics and not on aircraft in Alaska ...

 

MattS

MattS

Posted
Posted
12 hours ago, Noisemaker said:

Perhaps a slight aside, but after a cursory google search, I found nothing.  Is there a reason that a fully extendable tail wheel was not explored as a solution to the inherent problems of the tail draggers, rather than a nose wheel?  Obviously it would require a rebalancing of the centre of gravity of the airframe, but is there something that makes the idea unworkable?

 

The only thing I can think of is that when landing or taking off, the airplane needs to assume a tail-low attitude to tilt the wings to a higher angle of attack to generate the lift required. With a tall tailwheel, the airplane would need to be flying closer to cruise speed in order to "unstick". Likewise on landing it would either be unable to flare properly to arrest its descent rate, or would land with the tailwheel making contact while the main gear were still high off the ground, which I don't think is good structurally or for control.

 

I'm not an aero engineer or a real pilot so maybe they can shed more light on it.

istari6

istari6

Posted
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Posted
9 hours ago, chuter said:

That would be "Ice Window" installed along with the optional glycol de-icing system.  The idea was that if you had to use glycol to remove accumulated ice then you'd probably want to wipe at least part of the windshield off afterword.  A similar window could be found on some P-40E's (not in game), although it's mostly an "N" thing, and on some P-47 Razorbacks (again, not in game).  On the P-40N the window is the extra ~vertical frame (hinge) on the left side aft edge and the Razorback it's similarly the left side aft lower triangular area demarcated by its hinge.  The early Mustang used a wonky squarish window higher up the left side windscreen but not common.  The P-38 never had an ice window because it relied exclusively on hot air anti-icing as did most later aircraft.

 

That's really interesting, thanks.  So the idea is that the pilot used the glycol from the coolant system to splash the windshield, then they'd open the window in flight and reach through to wipe the screen?   

TheSublimeGoose

TheSublimeGoose

Posted
Posted
On 6/5/2020 at 1:40 AM, SCG_FeuerFliegen said:

 

Imagine how nice a P-39 would be with identical armament as a P-38.  Or even minus one or two .50s


The P-400 was that, minus x2 .50s. It had an M2 20mm cannon in the nose vice the 37mm, and x2 .50s (plus x4 .30s in the wings). As far as I know, the Ruskies didn't like it very much, although that may be because it had a neutered engine.

Armament or armament setup couldn't save the 39. The lack of a turbo killed it early, and killed it dead.

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Guest deleted@83466

Guest deleted@83466

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P400: "A P-40 with a Zero on its tail"

FeuerFliegen

FeuerFliegen

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2 hours ago, KotwicaGoose said:


The P-400 was that, minus x2 .50s. It had an M2 20mm cannon in the nose vice the 37mm, and x2 .50s (plus x4 .30s in the wings). As far as I know, the Ruskies didn't like it very much, although that may be because it had a neutered engine.

Armament or armament setup couldn't save the 39. The lack of a turbo killed it early, and killed it dead.

 

ah, yes I forgot about the P-400's armament; although being that the 20mm only had 60 rounds with the Hispano-Suiza, I wouldn't consider it the same armament as an AN/M2 with 150 rounds, and only having 200 rounds per gun for the .50s as opposed to a maximum of 500 rounds per gun, it just wasn't comparable armament.

 

I don't know if this would be possible, but imagine a nice turbo engine, tricycle landing gear (yes there'd be disadvantages, but much more room for ammo/guns in the nose), and a nice 20mm with 150-200 rounds, and 2x .50s with 500 rounds per gun.   I know it's hard to compare, but if they could fit two 13mms with 300 rounds per gun and a 20mm with 200 rounds in a 109, all squeezed around an engine, it makes me feel like the same could have been done with a P39 considering no engine was in that space.  But what do I know... I'm sure the engineers did everything they could with the knowledge they had at the time.

the_emperor

the_emperor

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4 hours ago, SCG_FeuerFliegen said:

I know it's hard to compare, but if they could fit two 13mms with 300 rounds per gun and a 20mm with 200 rounds in a 109, all squeezed around an engine,

well the German Aircraft Arms where often smaller and lighter compared to the allied (e.g. 42kg for the MG151/20 (incl. the electric/pneumatic recocking mechanism  while 60kg for the belt fed Hispano). On the other hand they lacked ballistic perfomance (lighter round with lower velocity), when you compare the MG131 to the M2 .50 and MG151/20 to the  Hispano.

So it was kind of a trade off, smaller and lighter weapons for perfomance.

TheSublimeGoose

TheSublimeGoose

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Quote

I don't know if this would be possible, but imagine a nice turbo engine, tricycle landing gear (yes there'd be disadvantages, but much more room for ammo/guns in the nose), and a nice 20mm with 150-200 rounds, and 2x .50s with 500 rounds per gun. 

I know it's hard to compare, but if they could fit two 13mms with 300 rounds per gun and a 20mm with 200 rounds in a 109, all squeezed around an engine, it makes me feel like the same could have been done with a P39 considering no engine was in that space.  But what do I know... I'm sure the engineers did everything they could with the knowledge they had at the time.

 


You're describing the P-63. Granted, it retained the 37mm cannon (although it used the slightly improved M10 vice the M4) but I do know some models were tested with a 20mm M2.

Also, apparently, if/when there were issues on the big cannon (in either the 39 or the 63), the Soviets would replace it with a B-20 20mm cannon or a 12.7mm UBS gun.

40plus

40plus

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On 5/26/2020 at 3:17 PM, istari6 said:

Yeah, that second video really brings out the whine we hear in game.  My old physics training taught that sound is energy being wasted.  I could imagine a damaged gearbox or one without oil (soon to be damaged :>) making this noise, but surprised that a well-oiled and properly functioning gearbox is so noisy. 

 

Could it be that straight cut gears were used rather than helical for the gear train. I recall watching in car videos of a track prepped BMW M3 that had straight cut gears for its final drive. The diff whine at speed was deafening. The advantage is an increase in performance as helical cut gears add friction to the drive mechanism through their sliding tooth pattern.

istari6

istari6

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2 hours ago, pfrances said:

Could it be that straight cut gears were used rather than helical for the gear train. I recall watching in car videos of a track prepped BMW M3 that had straight cut gears for its final drive. The diff whine at speed was deafening. The advantage is an increase in performance as helical cut gears add friction to the drive mechanism through their sliding tooth pattern.

 

Really interesting.  Thanks!  

69th_chuter

69th_chuter

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On 6/6/2020 at 10:48 AM, istari6 said:

 

That's really interesting, thanks.  So the idea is that the pilot used the glycol from the coolant system to splash the windshield, then they'd open the window in flight and reach through to wipe the screen?   

 

CORRECTION:

You know ... I got to thinking about this (its been a lot of years and my memory ... well ... ) and looked at these systems again and, no, the P-39 had it's own dedicated glycol tank in the nose alongside the 37mm receiver (the engine overflow tank was behind the engine in the aft fuselage) but the system for the P-40 that was tested drew from a "short straw" (upside down standpipe?) in the engine overflow tank but this system was NEVER produced, so the production P-40's actually never had a functional windscreen glycol deicing system.  (What kind of idiot would put THAT out there?)  And, yeah, if you could wipe the screen off that would be helpful as well, but by the war's start the Army apparently had decided that the most practical approach to an iced (or oiled) windscreen, although the P-39 kept its glycol, could be dealt with by simply opening the windscreen window and view the world through the opening, modern airliner style (not a lot of incoming airflow if the cockpit is/was reasonably sealed).

 

I apologize for the confusion.  ?

 

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