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  #11  
Old 06-12-2018, 09:17 PM
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Ed_Wischmeyer Ed_Wischmeyer is offline
 
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Quote:
Originally Posted by Low Pass View Post
For practical purposes, wouldn't the rotor wash be pretty much proportionate to the flying weight of the aircraft?
Let me try to answer that without blowing too much smoke. To get the air to push up on the aircraft, be it wing or rotor, the aircraft has to push down on the air molecules. If if can push down on a lot of them (high airspeed, large wing span), then the push is shared by lots of molecules and those molecules aren't pushed as fast. If there's only a few molecules (slow airspeed, short span, or lift concentrated at the tips because flaps are up), those molecules will get pushed harder and move faster, i.e., more wake turbulence.

That doesn't really explain it for rotors, but the bottom line is that rotor wash can be deadly to light planes, especially small ones like RVs. And don't ever think of flying formation with a helicopter in the lead...
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  #12  
Old 06-13-2018, 06:27 AM
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Agree with everything said. Give them or any large helicopter plenty of room. Fly above if possible. I flew CH-47s, and even that big thing does not like getting in the rotor wash of another. Watch helicopters in formation, they step up, not down, to avoid any chance of getting in rotor wash.
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  #13  
Old 06-13-2018, 07:16 AM
sblack sblack is offline
 
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Somewhere on youtube is a video of a student pilot land a cirrus (I think) shortly after a Blackhawk chopper has flown down the runway. The airplane is flying alonf fine and then suddenly it cartwheels, like a big invisible hand reached out and swatted it. I think the v22 is heavier i.e. worse. I never would have guessed that a heli could create that level of turbulence.

The student climbs out very slowly several minutes later. If he was ok at least he was badly shaken. Watch that vid and you will have a lot of respect for vortices that hang around after a chopper has been through.
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  #14  
Old 06-13-2018, 07:48 AM
Canadian_JOY Canadian_JOY is offline
 
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I was doing some avionics development work on the SH-60 Seahawk at Pax River when the V-22 first made its debut there for acceptance flight testing. Every point of observation, from standing on the ground to flying nearby, confirmed the V-22 to be in a substantially higher wake turbulence category than even a fully loaded SH-60. Maybe not the "factor of five" comparison made earlier but certainly more than "factor of two" compared to the SH-60. And they are loud when hovering.
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  #15  
Old 06-13-2018, 08:01 AM
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Quote:
Originally Posted by Beagle View Post
+1. To quote one of the Indiana Jones movies - You chose wisely.
I was an engineer on the V-22 program in the 80s (yes it has been around that long). Based on its weight and disk loading give it a good amount of time. A few minutes at least.
I remember the XV-3 that successfully flew in the early to mid 50s. Same basic concept.
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  #16  
Old 06-13-2018, 09:18 AM
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As a DoD guy in the Bell plant in Fort Worth (Hurst), I worked on the V-22 program. Before that, I worked in the test squadron at Edwards that was doing the flight test of the V-22. Wake turbulence from any helicopter is something to be wary of. I cringe when I see helicopters conducting training by hovering in the infield between the runway and the parallel taxi way. Watch aircraft as they pass abeam that operation. Obviously, it gets worse as weight increases.

We bought a Marine One version of the V-22. But I can assure you it won't be landing in the rose garden next to the White House.
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  #17  
Old 06-13-2018, 10:21 AM
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We had a V-22 parked on the ramp for months early this year due to an engine failure. He was traversing close to the airspace at night when a turbine failure occurred. To divert to KFLG the crew had to over-torque the opposing drive shaft and over heat TIT the remaining good engine. Still in a decent with crew aboard, the pucker factor was probably at max also while just making it to the runway. I'm sure the crew had a great time that night at the local Flagstaff bar!
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