XP-39 II - The Groundhog Day Thread

[buffnut453]

And Wagner's assessment was after only the first week of combat. If the P-39s were lighter and could get above the Zeros he wouldn't have needed any extra engine armor.

So you know better than the guy who was there and who was a credited ace to boot?

I'm lost for words.

 

[buffnut453]

Four .30calMGs with two synchronized is not much armament for a modern fighter.

I was assuming the ammo load weight for both the .30s and .50s was approximately the same.

It wasn't 4x30 cals. They only swapped out the wing guns (because the wing 50cals were unreliable). The nose 50cals were retained.

They clearly thought the mix of 2x50s and 2x303s was sufficient for the adversary they were facing.

 

[Ivan1GFP]

Ivan,

I wasn't the one pushing that idea, in fact I find it vaguely ridiculous. Other forum members were suggesting that American youth grew up with an inmate ability to resolve mechanical problems because every farmer had a beat-up Model T. It's an attempt to demonstrate American exceptionalism compared to other nations in an area where, frankly, it didn't exist.

Hello buffnut453,

I am not saying that the idea doesn't have SOME merit. What I am saying is that having experience working on tractors and cars and farm equipment in general may not necessarily translate to aeroplanes. Also, given the same opportunities, some people actually figure out what they are doing and some don't, but if more people are given the opportunity and necessity to experiment, some are bound to learn.

BTW, I know it is a typo, but your "inmate ability" had me laughing...... There is probably an element of truth to it though.

- Ivan.

 

[Ivan1GFP]

Visualize Koga's approach. He's touching down in tall grass with an unknown surface below. Because of his flat viewing angle, he's not going to catch the gleam of the water below. The slowest, softest touchdown with a taildragger is accomplished with an exaggerated three point landing, likely tailwheel first, and the engine ticking over a little above idle to aid in controllability. This was a one shot attempt, as his engine was practically out of oil and not likely to survive a go around.
As his tailwheel starts to drag in the tundra, the mains splash down, dig in hard, and flip the plane violently ass over teakettle onto its prop spinner then onto its back, capturing one prop blade underneath and sudden-stopping the engine. The main gear struts probably didn't come completely unglued until after the somersault impetus was well underway. I remember reading that one of the recovery party remarked that the landing gear struts were lying in rather odd locations, given the imagined gyrations of the aircraft.
Take a model of a Zero or other low wing taildragger and "hand fly" it through a couple table top three point landings, noting the angles at which the landing gears contact the surface. I think it will become self evident.

Hello XBe02Drvr,

Sounds like a plausible decision for a pilot in Koga's situation.... but for a few problems.
Go through the list of repairs again. Note the extensive damage to cowl and forward fuselage ahead of cockpit.
How is it possible with an engine idling to plant the spinner and flip the plane and plant one propeller blade vertically into the mud when the plane flipped and then only have one damaged propeller blade?
I don't believe the engine was turning any more when he touched down.

- Ivan.

 

[glennasher]

Back to P39s. Do I detect the sickly aroma of an expired equine carcass? My toes are bruised and bleeding; how about yours?

The aroma has long passed on, all that's left is the hide and bones.

 

[XBe02Drvr]

M

Note the extensive damage to cowl and forward fuselage ahead of cockpit.

In the words of forensic pathologists, "blunt force trauma". Once it stubbed its toe in the tundra, it would have bashed its nose in the mud as it flipped onto its back.

I don't believe the engine was turning any more when he touched down.

Then how do you account for the need to straighten twelve connecting rods? On a radial with that much rotating mass that's generally indicative of a sudden stop. The master rod in each cylinder row is massive and generally doesn't bend. Have you ever been inside one of these beasts?
Single engine planes generally don't have full feathering propellers, so even if the engine had quit running or was shut down it would still be windmilling. The bearings showed overheating but not seizure. Stopping a windmilling prop in flight requires holding the plane right on the edge of a stall for an extended period while engine compression slowly overcomes the aerodynamic windmilling effect, and is unachievable in some planes. A stationary prop significantly improves glide ratio, but is only useful when there's enough altitude to compensate for the loss due to the high sink rate while trying to get the prop stopped.

 

[FLYBOYJ]

If the P-39s were lighter and could get above the Zeros he wouldn't have needed any extra engine armor.

All I hear is "IF, IF, IF."

 

[XBe02Drvr]

(buffnut453)
Ivan,

I wasn't the one pushing that idea, in fact I find it vaguely ridiculous. Other forum members were suggesting that American youth grew up with an inmate ability to resolve mechanical problems because every farmer had a beat-up Model T. It's an attempt to demonstrate American exceptionalism compared to other nations in an area where, frankly, it didn't exist.

Hello buffnut453,

I am not saying that the idea doesn't have SOME merit. What I am saying is that having experience working on tractors and cars and farm equipment in general may not necessarily translate to aeroplanes. Also, given the same opportunities, some people actually figure out what they are doing and some don't, but if more people are given the opportunity and necessity to experiment, some are bound to learn.

I'm not claiming American technology was innately superior, certainly not to British or German, where we were a distant third or perhaps not on the podium at all, nor was I claiming tractor tinkerers would make instant aircraft maintenance technicians.
What I was saying is that given the size of our population and the degree of mechanical penetration of our society, we could summon a greater cumulative mass of hands-on knuckle- busting, greasy hands, and behind-the-wheel experience than any other nation on earth. Though I dislike the term "American Exceptionalism", if that is what it is, so be it.

 

[P-39 Expert]

So you know better than the guy who was there and who was a credited ace to boot?

I'm lost for words.

Are you arguing that less weight doesn't improve climb and ceiling?

Wagner had a little experience in the Philippines but his pilots had literally no combat experience and the vast majority were just out of flying school. He wrote three reports within the first 15 days of combat. He criticized altitude performance, the .30calMGs and the weak nose gear on the rough airfields. Altitude performance would have been improved by the deletion of the .30calMGs and other redundant equipment. And the AAF learned that paved or steel plank runways were necessary for the forward operation of all AAF planes.

 

[FLYBOYJ]

 

[buffnut453]

Are you arguing that less weight doesn't improve climb and ceiling?

I'm not arguing that less weight doesn't improve climb or ceiling. Clearly you're not reading what I'm writing...or you're deliberately misunderstanding it because you don't like the case I'm making.

I'm questioning whether the weight was necessary or not. You have consistently stated that the wing 30 cals and some amount of armour plate were unnecessary. That view is entirely contradicted by the man on the spot, Boyd Wagner, who clearly thought the 30 cals were necessary and he also asked for more armour plate for the engine. In short, the things you claim as unnecessary were deemed by the commander on-the-spot to be necessary.

Wagner had a little experience in the Philippines but his pilots had literally no combat experience and the vast majority were just out of flying school.

And you've assiduously ignored the RAAF example of 453 Sqn which reduced the weight of their Buffalos. None of those pilots, with the exception of the Squadron CO, had ANY combat experience prior to 8 Dec 41 and yet they made the weight reduction modifications around Christmas time 1941.

Again, if inexperienced Aussies could do it with the Buffalo, why didn't USAAF squadrons make similar changes with the P-39 when they were in combat for several months? The only logical explanation is that the people on the spot in PNG and Guadalcanal thought that the "extra weight" of wing 30 cals and armour plate was NECESSARY and not "useless."

 

[Ivan1GFP]

In the words of forensic pathologists, "blunt force trauma". Once it stubbed its toe in the tundra, it would have bashed its nose in the mud as it flipped onto its back.

Hello XBe02Drvr,

Can you show exactly how an upright aeroplane plants one prop blade, flips upside down and then ends up with the SAME prop blade dug into the ground??? I am having a very hard time figuring out the gyrations needed to make that happen.

Then how do you account for the need to straighten twelve connecting rods? On a radial with that much rotating mass that's generally indicative of a sudden stop. The master rod in each cylinder row is massive and generally doesn't bend. Have you ever been inside one of these beasts?
Single engine planes generally don't have full feathering propellers, so even if the engine had quit running or was shut down it would still be windmilling. The bearings showed overheating but not seizure. Stopping a windmilling prop in flight requires holding the plane right on the edge of a stall for an extended period while engine compression slowly overcomes the aerodynamic windmilling effect, and is unachievable in some planes. A stationary prop significantly improves glide ratio, but is only useful when there's enough altitude to compensate for the loss due to the high sink rate while trying to get the prop stopped.

I am not sure how the engine would stop either with significant forward speed. The only thing I can think of is that it seized because of a lack of oil when he was very slow before he touched down.
You mentioned overheated bearings. Do you have a more thorough repair list?

There were no bent connecting rods in the repair list I have. There were 9 bent push rods. Yes, I have seen the inside of a radial engine but I believe it was a R-2800 in a museum. Seen plenty of torn down auto engines and even helped rebuild a few. FWIW, I believe the Me 109 typically had full feathering props.

- Ivan.

 

[buffnut453]

I'm not claiming American technology was innately superior, certainly not to British or German, where we were a distant third or perhaps not on the podium at all, nor was I claiming tractor tinkerers would make instant aircraft maintenance technicians.
What I was saying is that given the size of our population and the degree of mechanical penetration of our society, we could summon a greater cumulative mass of hands-on knuckle- busting, greasy hands, and behind-the-wheel experience than any other nation on earth. Though I dislike the term "American Exceptionalism", if that is what it is, so be it.

In response to the question "Pre WW2 how many people had even driven a car let alone knew how they worked?" you wrote:

In the US and to a lesser extent, Canada, Australia and Germany, many. In the rest of the world, not so many. The US generation that fought WWII grew up between wars driving and tinkering on cars, trucks, tractors, and for some, even airplanes...You could call it "mechanical advantage". Even destitute poor folk like the Joads in Grapes of Wrath could find a way to acquire an ancient Model T Ford (converted to a pickup truck) in which to make their exodus to California, stopping along the way to grind the valves and fashion new head gaskets out of scrounged materials. This fostered a level of mechanical and operational experience and ingenuity on a broad scale that manifested itself in Construction Battalions, engine rooms, aircraft and tank maintenance shops, and a ready adaptability to aerial, mechanized, and naval warfare on a scale unmatched in the world.

It seems pretty clear to me that you were assuming a level of technical competence in certain countries based on ability to operate/maintain a car, the corollary being that other countries (including the UK) lacked that expertise. As I pointed out in the other thread, in 1940 the UK had the most mechanized army in the world. You don't get to that scale of capability if "not so many" people knew about machinery.

I believe the only significant difference was in the sizes of populations, not in the degree or extent of mechanical expertise. Circa 1940, the US had a population of 132 million while the UK had just 48 million so, unsurprisingly, the US was able to generate more mechanics. It could also generate more farmers, more mule drivers, more underwater basket-weavers, and any other number of professions.

If population size is a sign of exceptionalism, then India and the China had us beat decades ago.

 

[SaparotRob]

XBe02Drvr and I weren't inferring American Exceptionalism in the thread about "Exceptional CGI and the Battle of Midway" (or something like that - great thread Admiral!). We were discussing the loss of mechanically trained aircrews.
The United States, Britain and Germany all had a greater percentage of their populaces involved with machinery IMO. "Righty tighty, lefty loosey" has been ingrained into us since childhood. The draftees in Japan at that time were far less exposed machinery. Therefore, the loss of technically trained maintenance crews was a loss out of proportion for the IJN.
I've seen traditional rice farming up close and personal (from my hammock whilst smoking a maduro and quaffing a Coca-Cola). No technical experience required.

 

[XBe02Drvr]

There were no bent connecting rods in the repair list I have. There were 9 bent push rods.

MEA CULPA, MEA MAXIMA CULPA! My apologies. I rechecked the repair list, and you're right, it was pushrods, not conrods. Disregard all my previous conjecture about sudden stops. You're probably also correct about the increasing internal friction likely bringing the prop to a stop during the flare to landing. Large aircooled engines have their piston rings riding on a thicker oil film on the cylinder walls than the more temperature-stable liquid cooled variety. That's why they consume so much oil, and why the internal friction rises more rapidly with oil depletion. No "STP to the rescue" here.
Ptewy! Crow tastes awful! Even barbecued! Even Cajun style!

 

[FLYBOYJ]

The only logical explanation is that the people on the spot in PNG and Guadalcanal thought that the "extra weight" of wing 30 cals and armour plate was NECESSARY and not "useless."

Quoting the report from Buzz Wagner - "Lack of armor plate rear protection for the engine and the resultant high vulnerability are the greatest disadvantages of the P-39 type airplane. All P-39s shot down were hit in the engine and the coolant system."

If anything Wager felt the P-39 needed MORE armor, not less.

 

[buffnut453]

Crow tastes awful! Even barbecued! Even Cajun style!

Doesn't it just taste like chicken?

 

[SaparotRob]

Doesn't it just taste like chicken?

From personal experience I can tell you NO.

 

[XBe02Drvr]

Doesn't it just taste like chicken?

More like "bean porridge in the pot, nine days old"! Eye of newt and toe of frog for garnish.

 

[SaparotRob]

More like "bean porridge in the pot, nine days old"! Eye of newt and toe of frog for garnish.

That's how mom made it.