B-29 handling

U

Unit453

Guest
I'm climbing through 20,000 feet to a cruise altitude of 25,000. My air speed is around 265 mph at around 90% throttle. I opened the cowl flaps to get some air flow through to the radials (they were getting hot) and all of a sudden, it starts to nose up into a steep climb, until it eventually stalled. I've never had this happen before and it hasn't done it since. This is on the Wings of Power B-29. The aircraft was unloaded with about 12k lbs of fuel with no other load. The weather was clear. It took a minute or 5 to regain some kind of control of it. At 265 mph, there's no reason why it should have nosed up and started to go into a stall. It was climbing at 1500 feet a minute. At that rate, the higher the altitude, the faster my air speed was getting, progressively. I was gaining air speed, not loosing it up until that point.

I leveled it off and played around with the auto pilot after losing about 4000 feet. By this time, I'm hitting speeds of 350 mph with minimal throttle. I get the auto pilot working again and set it for a climb rate of 900 feet/min and she's fine from there, again, climbing through 20,000, except this time, the cowl flaps remained fully open at 315 mph.

Once at altitude, it eased the throttles back to 70% and never had a problem with it since. It struck me as kinda odd that opening the cowl flaps suddenly would throw the nose into a steep climb, even with the auto pilot engaged. An attempt to repeat it proved unsuccessful.
 
Turbulence? Bermuda Trapazoid? UFO enounter? System sneeze? If it was a one time occurance, I would chalk it up to a free thrill ride.
 
You quoting TAS instead of IAS? There should never be any reason to have the cowl flaps more than about 10% open, if at all in cruise. 90% power is more than the max continuous power under most circumstance. Getting hot, throttle back to 65% or so with appropriate RPM's. The max HP and speed specs quoted frequently are not sustainable! WOP and a few other sometimes model this in various ways. You might be able to disable this feature.

Good Luck! T.
 
I suspect that climbing at 1500'/minute at that altitude is also unreasonable with any kind of load.
 
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