Posted on 10/08/2007 12:33:53 PM PDT by Freeport
Bell Helicopter engineers have resolved a performance anomaly that test pilots had discovered when flying the hybrid aircraft in conventional flight mode, also known as the zero-degree position of the nacelles. The BA609 is a six- to nine-passenger corporate aviation tiltrotor, a product the companies expect to begin delivering in 2011.
According to Roy Hopkins, Bell's chief test pilot for the BA609, both prototype aircraft had been exhibiting a differential torque between the two prop-rotors in flight tests, causing a left-turning tendency at cruise speeds. The companies are flight testing one aircraft at Bell in the USA and the other at partner AgustaWestland's facility in Italy.
After being briefed on the quirk, Hopkins says Bell engineers homed in on the most unlikely of culprits - the placement of the exhaust port on the left engine. The aircraft's Pratt & Whitney Canada PT6C-67A turboshaft engines have a single exhaust port on the outboard side of the nacelle. The BA609's sibling, the Bell Boeing V-22 Osprey, has downward facing exhaust ports for its Rolls-Royce engines, and has not experienced a similar issue.
Further analysis and testing proved that turbine exhaust exiting the exhaust stack of the left side PT6C-67A turboshaft was swirling into the prop wash in a way that was causing extra drag on the left side. The same was not true on the right side of the aircraft where, due to the layout and direction of prop rotation, the exhaust flows into the slipstream.
The fix - extending the exhaust port farther down along the left nacelle - was put in place two weeks ago and tests were to resume in earlier this month. If cruise tests indeed prove the problem to be fixed, the company will install the correction into the Italian prototype, says Hopkins.
(Excerpt) Read more at flightglobal.com ...
I need one of those.
Yeah, me too.
> ... expect to begin delivering in 2011 ...
Only if it get certificated, which is far from certain.
The FAA presently requires that aircraft be able to
safely land with all engine out, from most flight
regimes (they already have exceptions for helo ops
off platforms).
Can this thing auto-rotate like a helo?
Guess: barely, and only if the blades are horizontal.
Can it glide like a fixed wing?
Guess: barely, and the touchdown speed will be
dangerously high.
Does pilot training include live demo of either?
Rotax has been flying on tether forever in part
due to this same requirement.
______
Gimli Gliders happen.
Make mine a regular Huey , the bugs are pretty well worked out and I only need two speeds ; slow and stop .
I wonder how hard it is to pilot the thing. I bet watching the owner take her up the first time is going to be fun to watch.
It’s probably so highly augmented, the owner/operator is just providing guidance and navigation.
Magnus effect.
Can this thing auto-rotate like a helo?
Guess: barely, and only if the blades are horizontal.”
My understanding is that, like the Osprey, as a forward flying airplane, it does not need to demonstrate auto-rotation, although other safety-landing requirements have to be met.
Don’t the props/rotors counterrotate?
Hmm, wonder if once, just once, those things might have crossed the minds of the engineers of a company that has been building helicopters since the late 40's.
Now, for all the naysayers who would prefer America should never take a risk and strive for greatness, here's a little Osprey porn for you: 1991 test fight.
The DM aerosafe eagle(google)has solved many of these problems that are listed for flight worthiness.
Looks like they do not.
Anyone read Time’s latest Hit piece on the military? Where they bash the Osprey? It’s on the front page of the bird cage lining magazine.
Cobra was smooth as glass , but an H model would be better for feeding my cows .
“of the nacelles”
Is that the thingy next to the dohicky?
Doesn't Rotax manufacture engines? I don't get the flying on a tether part. So solly.
Regards.
Bell YFM Airacuda circa 1940.
Yeah, right next to those rotating thingamagigs...
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