Having built an RV I can tell you that Van is very conservative. The designs are not tested to limits, but to what Van wants a plane equipped with the recommended power plant to be capable of safely accomplishing plus a safety margin. If the design is proven to meet those safety margins the testing stops! Planes that can exceed those limits such as the Harmon Rockets with IO-540's on RV-4's bother Van greatly, but they also prove that the planes can go far past VNE without flutter. There is a well known Dentist in the California Central Valley who has an RV-4 flying at least 50mph faster than the VNE with no flutter problems on an IO-360, but who knows how close to disaster he is flying. It doesn't seem unlikely that Van has a HUGE safety margin built into the design to compensate for hobbiest builders performing critical functions on fairly fast airplanes such as control surface balancing.

With that said one only has to look at the Lopresti Speed Merchants and the mass balance kit offered for Comanches stabilator to see that there is credibility in the TAS instead of indicated airspeed being the concern for flutter. The same Comanche airframe can raise the redline without beefing up the structure by adding this kit. Why would this be possible if the indicated airpseed is the limiting factor? Here is the mass balance kit for the Comanche and the listed increase in VNE. http://www.speedmods.com/pa24-htk.htm
Lastly, Ken Kruger is a very talented Aeronautical Engineer and frankly a genious. Beech would have been fortunate to have him if he had come along a few generations sooner.

Bryan

Assuming you can climb to that altitude, I think that's true of all airplanes.

But then, science wasn't my strong suit.

(I'm still trying to find out what is.)

I can't seem to be able to delete this post.

Jay,

Yes, the 25 was a hoot, and I believe you're correct. However, I thought we tried to keep a buffet margin a bit higher than 10kts in the Lear, but can't remember. We sure did in the airline business!

Jay,

Yes, the 25 was a hoot, and I believe you're correct. However, I thought we tried to keep a buffet margin a bit higher than 10kts in the Lear, but can't remember. We sure did in the airline business!

Was this the airplane that many operators added the "go fast" switch to disable the stick puller and/or Mach warning?

I was paid by the mile so speed was essential.

Because it lacked a mach trim mechanism the 20 series lear was limited to .74M with the autopilot disengaged. Most of these older planes had unreliable autopilots and yaw damp systems and were routinely hand flown at speed and altitude. To do this without going insane listening to the overspeed warning required that the warning be somehow silenced.

The later Lears had a mach trim system and thus could be hand flown to Mmo.

The only LearJets that got close to the coffin corner were some of the straight wing 20s and Century III 35s that had approval to operate up to FL510. This authorization was eventually stripped from the 20 series, limiting them to FL450 where there was an adequate speed margin.

I agree guys, the reason I brought up the 20 series Lear jets was the coffin corner issue, with the TN IO-550 in the Bo's they can get in to the FL's, and I am wondering if you can get into trouble with high/low speed stall (Coffin corner). I am not sure that I am phraseing my question right.

Jay

Bryan, I remember reading CAFE report on Dave Anders' RV-4. 250 mph on a modified IO-360 (about 235 hp) is quit an accomplishment.

I also agree with your comments re Ken Krueger.