Originally Posted by
NutLoose
That's just annoying.
P B Martin did his doctoral thesis on trying to cure the problem of the vibration of the MRB, pitch link cyclic loads and transmission vibration.... and then he did it again for Boeing. The cured the VR-7 dynamic stall hysteresis that affects the Cl, CM and CP, and makes a joke of being careful of the section design anyway, the dynamics coefficients have nearly no relevance to a static AOA idealized value. They resolved the hysteresis, but the drag went up by 50%. Was great if you added another engine. With the work I was doing separately, I discovered a device that also removed the hysteresis, and oddly reduced the drag as well. I tested that, and got it certified for the RHC, and then... we actually flew it on Franks test bed on the CMRB, on the SK-61 and also on the HH-3. Flew it on the UH-1H and various OH58s. Craig Whorley was the TP for Frank at that time, and we were given a blade to look at, and tried a simple proof of concept on the blade just to see how that would start looking. The blades had a substantial erosion issue immediately behind the nickel LE, from the transverse vortex structure... The limited testing showed an improvement at some points of the power required curve, in the first effort, at low and intermediate speed, but we didn't do much to help with the first guess at VNE, except for ONE THING. Craig commented that it was quite spooky to fly the SK61 without any vibration. We got busy with the B737 project at that time, and nothing much happened to the rotor, we never tried another configuration, I had tried around 50 configurations on the RHC, 1 on the H500, 1 on the 206, 1 on the UH1, etc.... and 1 on Franks CMRB.
We did get a curious outcome on the Enstrom with Enstrom,, before it was sold off to the Chinese. We got a slight power improvement in the hover, less than normal, for a fairly predictable rotor section (duh) but then we got a huge improvement in the cruise. That system is available if any of the OEMs want to proceed with it, we did develop a better erosion protection material, one that still degrades very slowly in particulate conditions, but survives without damage in rain. Nothing survives in rain impact, it is the most stunningly violent event on a section, but we did get the material.
I have no interest in doing STCs anymore, but OEMs are welcome to use my designs and materials if they so wish, I am just over dealing with idiot investors.
FDR
Oh, P.S.: the RHC power reduction was around 8% on the R22, and the R44 was around 5%, we tried only one config. The UH1 was 8%, as was the B206. The EN280 was 0.5" MAP recovery at the hover, and 2" in the cruise.
The stall RPM went down from 82% ref Nr stall to 77%, and there was a slight recovery of yaw authority at the stall Nr. The reason I went into the LE mod was that I was doing the TE mod when the rotors started to have disbond issues, and that seemed like an easy fix. The TE stuff followed what I had been doing on propellers for 15 years beforehand, which was TE mods. The 82% stall case for the reference with a LE and a basic TE mod went down to 68%, which was spooky. Not as spooky as the fact that at 68% I could do quite easy left pedal turns. When I set up the control position digital recording system (surprised Shawn but he got back by helping me with the OGE hover test point using the same.... That was pretty neat to set the controls and have the aircraft settle to the OGE hover without any other reference),. found the yaw pedal went from standard 100% pedal at stall of the Nr to 50%. The final fun factoid with the TE case was that with the TE modded, I could go to idle Nr, raise the collective fully, and then increase the Nr with the throttle, and fly off the pad. Couldn't do that with any other mod. It was stunning. Wanted to do that for the V-22, seemed like a fun thing, then ran into Ft Eustice's civilian speed bump, even with the assistance of Greg L from L-M APD...
So, to hear that Boeing is messing up the rotor for the CH-47F is just one of those annoyances. 160th SOAR, Boeing Vertol, BELL, if you want to fix your vibes and improve the performance of the helo, you can always contact me, I am done with fighting city hall.
The propeller mod we have done on literally hundreds of props, wanted to do that on the C-130, NIMBY rules, so the opportunity to improve performance went away, until there is a change of heart.
John Raisbeck was pretty interested in what we were doing, as was BLR's former boss before he sold out of the company. BLR would have been a good option, LORD was not.