Bombers and Agility

Thumpalumpacus said:

The Boeing 707 was barrel-rolled in a test-flight as well. Again, not much use in ops.

Click to expand...

Actually is was not a production 707 - it was a Boeing 367-80

FLYBOYJ said:

Actually is was not a production 707 - it was a Boeing 367-80

Click to expand...

Understood, it was a prototype that Johnson rolled.

The S.79 Sparviero was also quite agile. It was also a sort of 'hot rod' for a bomber. It could take off in 300m (don't know if will full load or with a somehow reduced one). As the Mosquito, it proved that wood still had its uses in aviation.

msxyz said:

The S.79 Sparviero was also quite agile. It was also a sort of 'hot rod' for a bomber. It could take off in 300m (don't know if will full load or with a somehow reduced one). As the Mosquito, it proved that wood still had its uses in aviation.

Click to expand...

"Had" for the period of WW2 and shortly thereafter. Not good for the long term

FLYBOYJ said:

"Had" for the period of WW2 and shortly thereafter. Not good for the long term

Click to expand...

Sure, it's a flammable material and it's also prone to be eaten by insects and fungi, though the second aspect can be at least mitigated with proper treatments. Still, what goes around comes around; cellulose may be gone out of fashion but other organic polymers and fibres are now displacing metals also in structural applications. All we had to do was to perfect what Nature already gave us

msxyz said:

Sure, it's a flammable material and it's also prone to be eaten by insects and fungi, though the second aspect can be at least mitigated with proper treatments. Still, what goes around comes around; cellulose may be gone out of fashion but other organic polymers and fibres are now displacing metals also in structural applications. All we had to do was to perfect what Nature already gave us

Click to expand...

I've worked on wood aircraft, difficult to repair and no longevity unless you're able to conduct continual maintenance and store the aircraft in a climate controlled hangar, not practical for today's combat aircraft - as far as "organic polymers and fibres are now displacing metals," I know of none used in primary structure of combat aircraft. Even the B-2, F-117A and F-22A have a degree of structural metal and I don't believe none of the composite structure are composed of "organic material (organic polymers)." If I'm wrong, please correct me.

FLYBOYJ said:

I've worked on wood aircraft, difficult to repair and no longevity unless you're able to conduct continual maintenance and store the aircraft in a climate controlled hangar, not practical for today's combat aircraft - as far as "organic polymers and fibres are now displacing metals," I know of none used in primary structure of combat aircraft. Even the B-2, F-117A and F-22A have a degree of structural metal and I don't believe none of the composite structure are composed of "organic material." If I'm wrong, please correct me.

Click to expand...

I think it is a semantics discussion. Organic chemistry is the study of chemicals that contain carbon, cows produce methane which is part of organic chemistry, they dont produce plastic which is another part. I dont know if carbon fibre compounds are officially termed "organic" but they could be and cellulose could be termed a type of carbon fibre.

Edit, a Boeing Dreamliner contains 35 tons of carbon fibre reinforced polymers which may come under orgainic chemistry, it certainly isnt wood.

Yup, carbon fibre is an organic material mainly made from polyacrylonitrile (C3H3N)n; with Rayon seldom used as well (another synthetic fibre, and even a quite old one, used since 1890s for women's stockings!). It's interesting that Rayon can be obtained from wood pulp by reprocessing cellulose. The beauty of organic chemistry is that you can make a wide range of materials from a handful of elements.

As for its usage in military aircraft, for example the vertical stabiliser of Mig 29 is of mixed construction (metal frame+ load bearing composite skin)

pbehn said:

I think it is a semantics discussion. Organic chemistry is the study of chemicals that contain carbon, cows produce methane which is part of organic chemistry, they dont produce plastic which is another part. I dont know if carbon fibre compounds are officially termed "organic" but they could be and cellulose could be termed a type of carbon fibre.

Edit, a Boeing Dreamliner contains 35 tons of carbon fibre reinforced polymers which may come under orgainic chemistry, it certainly isnt wood.

Click to expand...

Semantics - exactly!

That's my point - NO WOOD

pbehn said:

I think it is a semantics discussion. Organic chemistry is the study of chemicals that contain carbon, cows produce methane which is part of organic chemistry, they dont produce plastic which is another part. I dont know if carbon fibre compounds are officially termed "organic" but they could be and cellulose could be termed a type of carbon fibre.

Edit, a Boeing Dreamliner contains 35 tons of carbon fibre reinforced polymers which may come under orgainic chemistry, it certainly isnt wood.

Click to expand...

Kevlar and Spectra are organic compounds; so are the vast majority of composite matrices. None of these are natural, but hemp, sisal, and cotton fiber are being used as reinforcement fibers in secondary structure by several car companies.

If I recall from what I've read, wooden primary structure was strongly discouraged by the CAA after some airliner crashes in the late 1920s/early 1930s, so none of the companies that specialized in building large aircraft had any current expertise in manufacture of wooden structures.

swampyankee said:

If I recall from what I've read, wooden primary structure was strongly discouraged by the CAA after some airliner crashes in the late 1920s/early 1930s, so none of the companies that specialized in building large aircraft had any current expertise in manufacture of wooden structures.

Click to expand...

From Wiki...

"The late morning accident was arguably caused by the composition of the aircraft. The wings of Fokker Trimotors were manufactured out of wood laminate; in this instance, moisture had leaked into the interior of one wing over a period and had weakened the glue bonding the structure. One spar finally failed; the wing developed uncontrolled flutter and separated from the aircraft. In any case, the structural condition of the wooden wing is widely agreed to have been at least a significant contributory factor."

pbehn said:

A Lancaster loaded with a Grand Slam and extra fuel to reach the Tirpitz was dangerously overloaded, after dropping the bomb and burning off all that fuel it was a joy to fly. With two less turrets and most radio equipment taken out and uprated engines it was comparatively light and powerful. The plane in those two different conditions cant be compared to each other, so its even harder to compare to others.

Click to expand...

Except the Grand Slam was not dropped on the Tirpitz. Those were Tall Boys.

For an expert perspective on the Stirling, see Murray Peden's "A Thousand Shall Fall." Quite possibly the finest book written by a member of aircrew on the Bomber Command Experience. According to Peden, the Stirling's main flaws were the very high and unstable oleo legs and the short wingspan. The Airministry wanted to fit into the existing hangers. The Stirling could carry 12,000 lbs to the Ruhr but its ceiling was limited because of the inadequate wing surface. Peden quite liked the aircraft otherwise.

Jim

ThomasP said:

Hey Darthtabby,

If you have not already done so you might want to check out the pilot's manuals for the different bomber types. Pretty much all of the manuals will have a section titled "Flight Restrictions" or "Restricted Maneuvers". An example of this is the A-20A Havoc manual dated Mar'42:

Flight Restrictions

a. Maneuvers Prohibited:
Loop
Spin
Roll
Immelmann
Vertical Bank
Stall
Inverted Flight

b. Other Restrictions:
(1) Do not exceed 412 M.P.H. indicated airspeed.
(2) ......

Click to expand...

So much for the claims about being able to throw the A-20 around "like a fighter"! I haven't read the manual, but I did find a (somewhat cheesy) old War Department training film that emphasized that the A-20 was not an acrobatic aircraft or a dive bomber and advised pilots to limit bank angles and avoid violent pull outs from dives.

I also found a post on a flight sim forum where someone translated some restrictions from a He-111 manual. Seems the 111 was restricted to a maximum of 60 degrees when banking. (For comparison the A-20 video indicated that banking more then 75 degrees would subject the wings to forces they weren't designed to take, and that a 70 degree bank at 200mph would cause a stall. It also indicated that banking on one engine should be limited to 15 degrees and should always be in the direction of the functioning engine.)

11bwmech said:

Since you mentioned the B-36, which I worked on and flew in occasionally for over 5 years, I will repeat what I was told then: prior to air-to-air missiles but after the general use of jet fighters, the Peacemaker was presumed to be pretty safe at 40,000 ft. If the B-36 was flying at anything close to top speed, the only reasonable approach was from the rear. The big wing made it possible for the B-36 to turn so much tighter that the pursuer would be a mile or two away before completing its turn. Few fighters of that era (early to mid 50s) could reach that altitude with enough fuel to engage in a protracted dogfight. An F-89 pilot once said he could have gotten to a high-flying B-36, but he would have had to walk home.

Click to expand...

Thank you for sharing your experience. When you were working with the B-36s did they still have the original defensive armament or were they in one of the stripped down configurations?

From what I've read about the B-36 it sounds like the type needed a lot of maintenance?

Reluctant Poster said:

According to 8th AF studies the B-24 was a less accurate bomber than the B-17.

Click to expand...

Interesting. I would have guessed the B-24 would tend to be more accurate simply because it tended to fly a little lower on account of its inability to fly as high as the B-17.

B-24 was a leeetle lacking in directional stability and that is probably the cause of the accuracy problem. The M model and the similar PB4Y had a much larger single tailfin.

FLYBOYJ said:

[...] and store the aircraft in a climate controlled hangar [...]

Click to expand...

Bingo. Wood and moisture do not cooperate, and there's no magic paint to fix that. Wood expands and contracts with temperature, which will break any finish on it regardless of moisture absorption. And then once that finish cracks, guess what? We've introduced moisture into the equation. Now, the temperature ranges between sea-level and 30k are going to tax that finish, and you've got two temp cycles for every flight.

That's a lot of shrinking and swelling to tolerate, for the paint that's keeping the water from rotting the wood. There's not going to be nearly as much lifespan in such a plane compared to aluminum etc.

A couple of points. The Lancaster was, by all accounts an agile aircraft, as far as 4-engined Heavy Bombers were concerned. Dad flew Halifax II's and V's and didn't like them at all. These were older, clapped out aircraft but dad didn't like them at all. The Lancaster was by comparison, much more manoeuverable. Dad did the cork screw first on Halifaxes during training and also in the Lancaster on operations.

Second, when being chased around by the Nachtjagd, you didn't fly with the manual on your lap, or stick to the accepted manufacturers limits. You did what you had to to evade the aircraft. That often meant taking the aircraft up to and past its limits. Those who were too timid to do so, were shot down.

The Corkscrew, done properly was a particularly violent manoeuvere. I have the following accident report (Form 765 C) for KB.860, March 13, 1945. F/Lt Andersen reported "Normal Test Flight carried out. No unusual reaction during the test." Except that's really not what happened...

Dad was in contact with Vince Elmer, a member of the groundcrew servicing this aircraft. He was on this test flight. This is his account of what happened:

"You mentioned Andy Anderson. Once he finished his tour he came into the hangers and did all our test trip nights on the new aircraft and ones we did major inspections on. I flew with him on a number of these. One I will never forget and we talked about it down in Toronto a few years ago. One of his last tests when we had everything else checked out, was to put the Lane into a cork screw. This day we were away out over the North Sea. Any way I was ready for it and braced my self between the main spars. This time Andy did not pull out of it as quick as others. I finally slipped down on the floor and blacked out, although I could still hear. When he finally levelled out and I got my vision back, looking out we were just above the water. He also blacked out his rear gunner as well. To make a long story short we got back to base, signed the aircraft out ( about SPM at night in April) and went to eat. The next morning you could smell the petrol practically back to the mess. The skin was missing off the bottom of the main tank between the body and the starboard. inner and the tank ruptured. Further checks later the starboard. main spar was cracked.. I must add that I knew what a real corkscrew maneuver was after that."

This corkscrew manoeuvere was probably over the top. But dad did them on several occasions.

Dad also flew the B-24 Liberator (RAF version) on one Coastal Command operation. He said it was very difficult to fly. Very heavy on the controls.

Jim

Further to the above post, please see attached comments by Schnaufer on the Corkscrew Manoeuvre. This from a post war interogation.

One thing I discovered from looking at flight test data is that pilot technique can make a vast difference in the loads for exactly the same maneuver, at least in the world of rotorcraft. When I was at Sikorsky, the flight test engineers would tell of a USArmy test pilot who would perform buttonhooks (basically, overfly a spot at high speed, pull up and turn sharply and return to the same point from a different angle) and show lower vibratory loads on the airframe than some "green" pilots would in level flight. Of course, helicopters are weird (albeit more awesome than fixed-wing ones), but I think the same would apply to fixed-wing aircraft: a more experienced pilot could "throw" an airplane around in ways that seem more violent than a less-skilled one and actually put less stress on the airframe. Witness what somebody like Bob Hoover could do with a business twin.

pbehn said:

One of the leaders of 617 squadron encouraged pilots and crews to practice aerobatics. He had been blown upside down on a raid, he thought that being upside down for the first time while on a raid was a bad idea. He also encouraged crews to practice violent evasive maneuvers in daylight so the whole crew knew what to expect and what to do as far as opening fire and stopping firing went.

Click to expand...

And 617 used Lancs as Pathfinders so that suggests extreme maneuvers were approved in that unit at least