Warbird Information Exchange

Can anyone give me ballpark grass strip requirements for the North American B-25 vs Douglas A-26 ? Both in light trim, etc.

Don't know the answer to your question, but I think I remember hearing somewhere (once upon a time, etc.) that the North American B-25 Mitchell was notorious for relatively weak landing gear and/or was prone to failures there. If that is true, it might not be a good idea to try to operate one routinely off of a unpaved airstrip.

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I have seen numerous B-25's and A-26's successfully land on and take off from the grass strip at Geneseo NY. One or both of those types has attended the airshow there almost every year since 1984. So I don't think that either aircraft has a problem with unpaved airfields... remember that when those planes were designed, grass strips were the norm and that as combat aircraft, they had to be able to handle difficult conditions. (Although I have never heard the Geneseo strip described as difficult by anyone; in fact I have seen a Lockheed Constellation and Douglas C-54 on that field, two types that were designed for paved runways.)

We used to go into Hope BC airfield (grass) and fill the B-25 up ,mains and auxs ,because the fuel was cheap. Used the grass runway at Vanderhoof BC because it pointed in the direction we were going.Obviously,the A-26 would use more length but I have no direct experience on grass with this type.

Sorry, I forgot to answer the question, 4000ft at sea level was comfortable in the B-25, I would guess that the 26 would like 4500 to 5000.

The B-25 is not notorious for weak landing gear per se, but it is notorious for a weak nose gear, as that is the weakest part of the whole aircraft. When you see B-25's land, there is a reason why you see the pilots hold the nose off as long as possible. That is because the nose gear is weak and they are trying to minimize the stress on it. Part of it is also to aerobrake with the nose in the air to use parasitic and induced drag to help stop the aircraft and thus save the brakes. The B-25 operated off of many grass strips and unimproved runways with no problems during the war, and the type continues to do so. Kermit Weeks used to fly his B-25 off of his grass strip with no problems until he stopped flying it some 10 or 12 years ago or so.

As far as what runway length to operate it off of, that requires a whole lot more information - namely, what density altitude and what weights are you talking about - lightweight, medium weight or heaveyweight? Also, are you talking about war-time scenarios or modern scenarios, as there is a huge difference between the two. Remember, during the war they used to fly the B-25 at or sometimes more than max gross weight, as dictated by mission requirements. In modern ops, all B-25's operate at much, much lighter loads. Obviously, lighter loads improve performance quite a bit.

I don't know much about the B-26 other than to say it is a much "hotter" or faster aircraft. The biggest difference between the two is that the B-26 has a laminar flow wing whereas the B-25 doesn't. Traditionally speaking, laminar flow wings take longer rolls for takeoff and landing because of the higher speed unless the wing is attached with high lift devices such as leading edge flaps/slats. When you hear "laminar flow", just think jet, as most modern jet aircraft utilize laminar flow wings.

I have flown the B-25 numerous times. The nose gear is not as robust as the mains and since I'm currently flying the A-26,the same can be said about it. Will they both land and take off on grass, sure. The real question is if it advisable. The flight manual says to avoid any depressions more than 6 in wide and has many restrictions on towing the A-26. This is because of potential internal damage to the nose gear. We found that the centering cam had been banged into the inner chrome of the strut enough that it was pitted and would not hold fluid or nitrogen. This is caused by hard starts and stops during towing or by taxiing on rough surfaces. So grass strips need to be very smooth in order to avoid this. 5000 ft is our minimum length in concrete. Grass would require more. The laminar flow high speeds wing required the first slotted flaps to reduce the speed for landing. This makes the landing technique different from the B-25. The stall in this configuration dumps the nose briskly downward which would be disastrous 10 ft over the runway. The airplane is flown on to the runway with power in nearly a three point landing. The nose will slam down if flown like a B-25 landing with the nose high. Not conducive to longevity of the strut. So consequently, the two A-26's I'm associated with operate on concrete only. JR

Thanks for all of the info. I'm mainly interested in a modern lightweight trim scenario for both aircraft. I was curious how the requirements stack up against a P-51 as well, which I've seen operate out of 2600 ft grass strips with good approaches at ease.

Thanks again for the info.

At some point, you begin to worry about giving yourself bigger margins on a very expensive and dangerous piece of equipment. I'm sure a B-25 *could* be operated off of 2,000' with good approaches, but that wouldn't be a recipe for a long happy life for the airplane or its occupants. An engine burp after liftoff or a braking glitch and bad (or worse) things could happen.

And the insurance folks come into play at some point. IIRC, Aluminum Overcast is restricted to 100' wide runways of over 5,000'. That's far in excess of the aircraft's needs on a normal day, but substantially increases the margins when something doesn't go according to plan.

I know when we had a B-25 and B-26 based locally, both were comfortable on the 5,000 paved strip and they took the B-25 to shorter fields. I don't remember them taking the B-26 to shorter fields.

Lynch Air Tankers developed the Lynch STOL 26 for the Lynch A-26 fire bombers.
Technically designed to compensate for density altitude, it would still have affects on an empty lightweight A-26.

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4-5,000 feet for a B-25??




Sorry, couldn't resist. Back to hiding for me.

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Again, it's hard to say because performance requirements are very complex and depend on many, many variables and assumptions. With that being said, different operators have different comfort levels based on their background and experience. From the many B-25 operators I've talked to, the "comfort zone" for most is in the range of between 3500 to 4500 feet. One Mitchell pilot I talked to said the shortest strip he ever operated off of was 2800' long. I think that's a little short for most though. If you want actual numbers out of the manual I can get that, but it will be a week or two because I'm not at home presently.

Exactly! When you operate a rare and expensive piece of machinery, you are ALWAYS doing risk analysis. Sometimes the reward is worth the risk and sometimes not. That's strictly a choice up to the Pilot-in-Command and what they are comfortable with. By operating out of longer runways you are giving yourself a much larger buffer in case something goes wrong. Just because the pilot manual and/or numbers say you can do something doesn't necessarily mean you should do it. Any good pilot worth their weight will always have safety as their number one interest. Remember, during the War, all bets were off to accomplish the mission. Planes and crews were effectively "disposable". Thank goodness we're in peacetime now and safety takes priority over the mission.

I can give you 10 reasons why that is an invalid comparison to what we're talking about, but I think you already know the answers.

The jump off the Hornet could not have been done in the B-25 except for the special conditions present when they launched. The wind was howling, the ship's forward speed added to the relative wind and the start of the roll was made when the deck was pointed downhill. They were lifting off about 85-90 mph, indicated. There is why they were all very courageous. The minimum safe single engine speed in the loaded B-25 is 145 mph. If an engine had so much as sputtered at 85, it would have rolled over on its back and crashed. The only option to stop this would have been to pull the power off the good engine, crash land into the sea and hope the carrier doesn't run over you. At the same time, there was very little room for the left main gear to stay on the deck and only about 6 ft of right wing tip clearance from the carrier's island. The B-25 does not have nose wheel steering. It is normally done with brakes and differential power. Brakes obviously were not an option on the short deck. I have done several Vmc demos in the B-25. Each time only increased my admiration for those brave men. Having known Gen Doolittle, he made the big difference in leading those guys off the deck to show them it could be done. Fortunately, 32 engines performed well enough that all made it. Doolittle said it best "l could never be so lucky again!" And I consider myself lucky to have met several of the Raiders and fly the B-25. JR