Groundhog Thread Part Deux - P-39 Fantasy and Fetish - The Never Ending Story (Mods take no responsibility for head against wall injuries sustained)

fubar57 said:

I read that the breakaway from grass was due to heavier bomber introduced though I can't recall the time frame

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Well it pretty much started with the start of the war, ironically assisted by the blitz, the rubble of bombed out cities and towns was used for the hard core. Of course bombers were the heaviest, but fighters were busy gaining weight, the Spitfire doubled in weight while P-47 and Typhoon were the weight of light bombers of a few yrs before. Runways/taxiways and hard standing built in UK were equal to building a highway to China.
During the years 1939 to 1945, four hundred and forty-four Royal Air Force airfields were constructed in the United Kingdom with paved runways, perimeter tracks, and hard-standings. During the peak construction year of 1942, with a labour force of sixty thousand men, new airfields were being turned out an average rate of one every 3 days in addition to sixty-three major extensions to existing stations (Hudson 1948:5). The whole of the airfield projects were planned administered and supervised by engineering and technical staff operating directly under the Directorate General of Works of the Air Ministry, with the construction work carried out by British contractors. In the early stages of the war programme, the Air Ministry were far sighted enough to select and encourage several major contractors – W&C French, John Laing, Robert McAlpine and George Wimpey. It was on the foundation of these contractors that the airfield construction was based and from which grew a contracting army. Overall in the five years of war, one hundred and thirty six contractors were engaged on a total of eight hundred separate contracts ranging in value from £25,000 (£750,000) to over £3.5m (£105m.) "Six contractors between them, carried out one hundred and ninety-six contracts of major value" (Hudson 1948:44). These projects required large earthmoving operations, on average involving 500,000 cubic yards of earthworks but on special sites up to 3,000,000 cubic yards. By 1942 this vast operation was utilising heavy American plant of the crawler, tractor and scraper type together with British equipment. The paved runways were mainly constructed using concrete paving with or without asphalt or tarmacadam surfacing. In all cases the necessary war-time controls of materials, plant and labour made the site planning and programme of work very much the concern of the Air Ministry. Furthermore, as contractors, particularly smaller firms, were unable to obtain the total plant required for the airfield work by 1944 the Air Ministry had become holders of considerable quantities of construction plant obtained under Lend-Lease or by allocation controlled by a Central inter-Departmental Committee. The Air Ministry holding included, but was not limited to 360 tractors and bulldozers, 250 excavators, 34 scrapers, 406 rollers, 5,300 tipping lorries, 220 dumpers, 150 concrete mixers, 500 power pumps (Hudson 1948:45) from here http://www.arcom.ac.uk/-docs/proceedings/ar2009-0847-0856_Potts.pdf

I don't think Henderson was provided with steel matting until early 1943.

most of the airfields in the northern territory remained dirt strips for nearly the entire war. There a few exceptions

not all that relevant bu the airfield at RAAF Pearce was sealed from almost the beginning of the war. conversely the training fields at pt cook were unsealed. Amberley was unsealed. Townsville was unsealed until the latter part of 1942

I unsure about Cooktown

Milne Bay in 1942 was unsealed and had no steel matting until months after the battle

Milosh said:

Berry Airfield (12 Mile Drome)

The airfield was constructed in early 1942, being completed on 15 May. The airfield had an 8-inch base of crushed rock and pit gravel for a single earth runway approximately 4,500' by 150.

40th and 80th FS USAAF with P-39s stationed there.

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Apparently there were 7 or 8 airdromes eventually built in the Port Moresby area, I say airdromes because several of them had more than in runway.

3 mile was the first being built in 1933 although expanded considerably later. It wa operating A-24s in March of 1942 and P-39s in May (30th?).
7 mile was operating P-39s in June of 1942. This was another prewar field enlarged during 1942, it is the one used by the B-17s in 1941, it was used by the RAAF squadron 75 in March of 1942 but was used mostly by bombers.
12 mile was covered by Milosh.
14 mile went into service in Sept 1942 as did 17 mile. 14 mile operated mainly fighters with a few B-25s and 17 mile operated mainly B-25s with a few fighters.
30 mile went into service July of 1942 but it's intended PSP planking had been used elsewhere and it was used used as a fighter strip and emergency landing field. At some point it did acquire PSP planking but only 3 US fighter squadrons were ever based there.
5 mile went into service in Jan 1943.

Some of these airdromes wound up with interconnecting taxiways.

As soon as the bridgehead was taken and secured after D-Day engineers started constructing matted runways, it may have been possible to operate fully loaded Typhoons from grass, it certainly wasnt the desired option, I cant imagine US forces were any different.

In Great Britain the grass (or sod) fields were responsible for the pre-war requirement that tyre pressure no exceed 38lb/sq/in regardless of what type of aircraft. This was to avoid putting runts in the fields. Depth of penetration of the tyres into the field was either 1 or 2 inches (going by memory) and obviously this was inadequate as the plane's weight rose.

Point is that many of these "grass" airfields bore about as much resemblance to front line airfields as a golf course fairway does to a farmers meadow. And front line airfields could vary tremendously depending on theater and country building the airstrip.

From Wiki so................"On Pacific islands the matting was typically covered with crushed and rolled coral or soil to form a level surface. The perforated and channeled design of the matting created strength and rigidity and facilitated drainage. A runway two hundred feet wide and 5000 feet (1500 m) long could be created within two days by a small team of engineers." Now this could very well be on an site that was already bulldozed, filled and rolled/compacted.

Shortround6 said:

In Great Britain the grass (or sod) fields were responsible for the pre-war requirement that tyre pressure no exceed 38lb/sq/in regardless of what type of aircraft. This was to avoid putting runts in the fields. Depth of penetration of the tyres into the field was either 1 or 2 inches (going by memory) and obviously this was inadequate as the plane's weight rose.

Point is that many of these "grass" airfields bore about as much resemblance to front line airfields as a golf course fairway does to a farmers meadow. And front line airfields could vary tremendously depending on theater and country building the airstrip.

.

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I think in UK peacetime it could be tolerated when an airfield was unfit to fly, once a war is declared that situation cannot be allowed. Any grass airfield that has had constant rain for weeks will just turn to mud. The BoB was famously fought in a glorious summer, that weather doesn't continue all year around.

Ivan1GFP said:

on uneven ground airfields the nose strut vibrated and often broke, which made it necessary to limit the taxi speed.

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Not alone in that department. Most "nose draggers" had that problem to a greater or lesser extent.
Pre-1975 Cessna 182s were notorious for that, as they had the nose gear strut attached directly to the firewall, a heavy engine, and inadequate elevator authority to keep the nose light while taxying. If you hit a "hollow" while taxying off pavement, you could bottom the strut, bang the prop into the ground, sudden stop the engine, and bend the firewall. An expen$ive mi$take for $ure! Off pavement landings were a no-no. Naturally, this created a boom market for aftermarket STC modifications, most of which were later incorporated into standard production aircraft.
Cheers,
Wes

Aleutian fields were notoriously bad. The field at Adak was built by filling in a tidal lagoon with crushed rock. Flooding was common. Willawaws could peel up the PSP and roll it back like it was paper.

Shortround6 said:

This was to avoid putting runts in the fields.

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Whasamatter, you don't think undersized piglets make good fill? Cummon, man we gotta work to overcome our prejudices!

XBe02Drvr said:

Whasamatter, you don't think undersized piglets make good fill? Cummon, man we gotta work to overcome our prejudices!

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I suspected a baconist comment but wasn't sure, anyway, I am now in a safe space, so all is OK.

I barely passed typing in high school and that was 50 years ago, haven't gotten any better.

Shortround6 said:

I barely passed typing in high school and that was 50 years ago, haven't gotten any better.

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I never even had typing in high school and I haven't gotten any better, either.
Cheers,
Wes

XBe02Drvr said:

Not alone in that department. Most "nose draggers" had that problem to a greater or lesser extent.
Pre-1975 Cessna 182s were notorious for that, as they had the nose gear strut attached directly to the firewall, a heavy engine, and inadequate elevator authority to keep the nose light while taxying. If you hit a "hollow" while taxying off pavement, you could bottom the strut, bang the prop into the ground, sudden stop the engine, and bend the firewall. An expen$ive mi$take for $ure! Off pavement landings were a no-no. Naturally, this created a boom market for aftermarket STC modifications, most of which were later incorporated into standard production aircraft.

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Hello XBe02Drvr,
Perhaps it is a similar problem you are describing and perhaps it is not.
Note that your description was for a prop strike and bending the STRUCTURE to which the nose gear was attached.
This is clearly not the case here, because the description is for breaking the strut rather than the structure to which it was attached.
Note also that the Airacobra actually had enough elevator authority to raise the nose wheel at 50 MPH (from NACA L-602).

I don't really keep track of these kinds of failures but the only other aircraft that I have heard that tended to break the nose gear was the B-26 Marauder. There is mention of excessive (unsafe) vibration of the nose gear on the B-25 Mitchell if the damper was not functional, but not a pattern of breakage. There is also no mention of this as a problem on the P-38 Lightning either.
Without the damper, the Mitchell apparently would vibrate badly enough to pop loose the rivets in the nose structure.

- Ivan.

Ivan1GFP said:

Perhaps it is a similar problem you are describing and perhaps it is not.
Note that your description was for a prop strike and bending the STRUCTURE to which the nose gear was attached.
This is clearly not the case here, because the description is for breaking the strut rather than the structure to which it was attached.
Note also that the Airacobra actually had enough elevator authority to raise the nose wheel at 50 MPH (from NACA L-602).

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Whether it breaks the strut or the firewall is immaterial from an operational perspective. Sure it matters to engineers and mechanics, but the issue here is how to keep it from happening? Pilots are taught to keep the nose "light" when taxying off pavement. Easier to do in some aircraft than others. Frankly, I'm surprised to hear that the Cobra had no elevator authority below 50MPH. You'd think that with its aft CG, it would be easy to "rock back" on the ground with a little propwash over the elevators. So you have to ride the brakes, keep the stick back in your gut, give her a little power, and try not to pick up too much taxi speed while keeping the nosewheel as light as you can, and praying. Must be the Cessna 182's ancestor.
Cheers,
Wes

XBe02Drvr said:

Whether it breaks the strut or the firewall is immaterial from an operational perspective. Sure it matters to engineers and mechanics, but the issue here is how to keep it from happening? Pilots are taught to keep the nose "light" when taxying off pavement. Easier to do in some aircraft than others. Frankly, I'm surprised to hear that the Cobra had no elevator authority below 50MPH. You'd think that with its aft CG, it would be easy to "rock back" on the ground with a little propwash over the elevators. So you have to ride the brakes, keep the stick back in your gut, give her a little power, and try not to pick up too much taxi speed while keeping the nosewheel as light as you can, and praying. Must be the Cessna 182's ancestor.
Cheers,
Wes

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Is it possible that this was just part of the learning curve with tricycle undercarriage? Later designs built on what was learned.

XBe02Drvr said:

Whether it breaks the strut or the firewall is immaterial from an operational perspective. Sure it matters to engineers and mechanics, but the issue here is how to keep it from happening? Pilots are taught to keep the nose "light" when taxying off pavement. Easier to do in some aircraft than others. Frankly, I'm surprised to hear that the Cobra had no elevator authority below 50MPH. You'd think that with its aft CG, it would be easy to "rock back" on the ground with a little propwash over the elevators. So you have to ride the brakes, keep the stick back in your gut, give her a little power, and try not to pick up too much taxi speed while keeping the nosewheel as light as you can, and praying. Must be the Cessna 182's ancestor.

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This is getting interesting.
The question of what breaks first is important because with sufficient stress SOMETHING will certainly break.
Greg Boeser stated that the Airacobra had a fragile nose gear strut.
The account from the Russian link makes the same assertion, so I believe this is pretty good support.

You believe that the Airacobra did not have enough elevator authority below 50 MPH.
The NACA engineers seemed to think the elevator authority was quite good if the Airacobra could lift its nose wheel off the ground at only 50 MPH. Remember that its stall speed clean is 105 MPH....
Your statement of fault with a prop strike or the possibility of something else breaking if the aircraft should encounter a dip in the ground sounds like a characteristic of ANY aircraft equipped a nose wheel if it should take a hard enough bump and seems related to the Airacobra only in the fact that it had a nose wheel.

- Ivan.

Greg Boeser said:

That long nose wheel strut was a bit fragile for rough fields though.

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I though so too but watch John Hustons wartime film on the Aleutians. P39s were literally swimming in water. Henderson field, New Guinea and frozen lakes in Russia. They were tough little birds and no tail dragging.

Barrett said:

Sidebar: Just received a review copy of the latest in the Osprey "Duel" series: P-39/400 v. A6M2. Amazingly enough, the Bells broke even at 15-15 in New Guinea though of course they claimed 5-6 times as many.

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The Aleutians got the P39 20 kills to one combat loss albeit against Rufes and larger seaplanes mostly

parsifal said:

P-39s never even came close to shooting down 15 Zekes over Moresby. Try a maximum of 7, but probably closer to 5,

Ratios for overall P-39/A6M losses are better. All up losses are around 30 for the Zekes to about 60 for the P-39s, though some sources say many more.

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The commanders figured out you flew full speed 500 feet off the ground and strafe the Japanese airfields. The Japanese would have a few Zeros on patrol but usually could only have a minute or two to maneuver to attack. Zeros were faster with airspeed gained in a dive but not in level flight. The P39 could just throttle up and leave the fight. If luck was with the P39s they could bounce Japanese planes on takeoff and blast them. The Japanese did not armour up their planes so a few hits and flames galore.

Shortround6 said:

It is interesting but flawed, it doesn't really say how the planes were were used (tactics or combat situation) and relies on the rather dubious method of comparing the scores of the top aces. I am not trying to get into an argument about claiming or over claiming or anything like that.

The method is dubious because it fails to take into account the number of missions flown by the pilots of each type and number of times each pilot was actually engaged in combat. As an extreme example we have Eric Hartman who (according to wiki) He "flew 1,404 combat missions and participated in aerial combat on 825 separate occasions." to get is 352 victories.
This article does not tell us how many combat missions the various pilots (of several air forces) flew or how many of those missions resulted in actual combat.
The US in particular tended to rotate pilots out of combat after a fixed number of missions (although many extended their tours voluntarily or signed up up for a whole new tour, same with many British pilots, including the commonwealth).

So if you have a Russian pilot who flew plane A on 250 missions and engaged in combat (fired guns?) 175 times and claimed 50 victories how does that prove that Plane A was better than Plane B that was flown by An american pilot 120 times and fired it's guns 75 times and shot down 30 planes? (made up numbers)

Please note I am not trying to take anything away for Hartman or any of the pilots listed in the article. In many cases it was a testament to luck, skill and day in day out courage simply to survive 100 mission let alone several hundred. Shooting down substantial quantities of enemy aircraft is a whole different story.

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Hartman shot alot of old aircraft to cut his teeth in the early part of the war. Gaining experience and knowledge. Wonder what he thought of the P39?