.....Not so.
....also 600,000lb/ft from a tail rotor? Not so.
But off topic. Sorry to dump this on the thread.
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Of couse in case of Helo, some tail rotors 'pull' into fuse and others 'thrust'. An imbedded tail rotor simplifies the aerodynamics of the tail rotor. 'lose a tail rotor and you can kiss your ass goodbye if you have any altitude at all. Very bad 'thing'. It has been a very long time but I believe the King Cobra at Bell had a rotor system delivering 600,000+ foot pound of torque...
Main rotor. Unrestrained when tail rotor lost. Ship rotates violently in the opposite direction from main rotor......Not so.
....also 600,000lb/ft from a tail rotor? Not so.
But off topic. Sorry to dump this on the thread.
IIRC, in another thread that touched this topic, consensus was reached that improved performance in high AOA/high G turning and pull up situations was deemed more important than single engine handling.As FLYBOYJ said, with counter rotating props there is no critical engine, or both engines are critical, depending on how you view it. Everything I have come across seems to indicate that the change to outward was to increase stability, and that P factor was not a decisive factor.
Main rotor. Unrestrained when tail rotor lost. Ship rotates violently in the opposite direction from main rotor.
I've had two hours stick time in a Jetranger, mostly cruise, but with a few transitions and a couple scary attempts at hover, and the idea of an 80 knot roll on landing with no tail rotor is downright terrifying. The IP, our company's RW chief pilot was calm, collected, and encouraging throughout, but my boss, the FW chief pilot riding in back, was a nervous wreck and finally ordered me to give the ship back to the IP for the rest of the trip. He was kind of a PITA type, and I have to admit I was relishing his discomfort.All returned and landed safely using run on landings.
I've had two hours stick time in a Jetranger, mostly cruise, but with a few transitions and a couple scary attempts at hover, and the idea of an 80 knot roll on landing with no tail rotor is downright terrifying. The IP, our company's RW chief pilot was calm, collected, and encouraging throughout, but my boss, the FW chief pilot riding in back, was a nervous wreck and finally ordered me to give the ship back to the IP for the rest of the trip. He was kind of a PITA type, and I have to admit I was relishing his discomfort.
Cheers,
Wes
It's hard to imagine, with its relatively short tail boom, skimpy vertical stabilizer, and fragile looking skids. OTOH, one of my RW-to-FW conversion students reputedly pulled it off in a Charlie gunship on the Marston at Chu Lai back in the day. (I didn't learn this from him. Some of the Huey jocks in our local Army Guard say he was a legend who got a Silver Star for some of his exploits in 'Nam.)I could not tell you if tail rotor loss was recoverable in a 206 or 407.
Chris I should have been more specific and pointed to Bell w/two blade articulated rotor system and no rudder. That said, just about any helicopter with single rotor system at low airspeed is in deep trouble.Depends on your airspeed and condition of flight. For instance the loss of tail rotor emergency procedure in a Blackhawk was to remain above 80 kts and perform a roll on landing. I'll have to look at my checklist when I get back home from my Germany vacation in January to verify, but that is what I recall it being.
I used to work in the off-shore helicopter industry as well, and we had helos lose their tail rotor control and effectivity over the Gulf, fly one hour back to the airport and safely perform run on landings. The S-92 had a design flaw with the tail rotor bearing, and it tail rotor loss occurred to several of them. All returned and landed safely using run on landings.
Of couse in case of Helo, some tail rotors 'pull' into fuse and others 'thrust'. An imbedded tail rotor simplifies the aerodynamics of the tail rotor. 'lose a tail rotor and you can kiss your ass goodbye if you have any altitude at all. Very bad 'thing'. It has been a very long time but I believe the King Cobra at Bell had a rotor system delivering 600,000+ foot pound of torque...
A Bell 212,
With an 1800shp twin pack loses roughly 200hp through the drive-train (transmission loss) and has a 1294shp txmsn limit. But assuming theoretically it was delivering 1600shp to the main rotor that works out to roughly 26,000 ft/lbs of torque one foot from the mast (though the blade tips would be making considerably more).
A conventional two bladed tail rotor which all the civilian Bell helicopters utilise, that were developed from the UH-1 (including the B412 with the four blade MR Head) would only use (again roughly) less than 20% of the total power (at low speeds and in the hover). A fenestron type of tail rotor can absorb up to 25% of total power in the hover but next to zero above about 40knots.
If you lost tail rotor drive in flight with any conventional helicopter type (single main rotor, conventional t/rotor) in straight & level cruise there would be a slight yaw and mild pitch change but there wouldn't be any need for a change of underwear.
In a fenestron type heli, you wouldn't know about it in a stabilised cruise until you made a power, or attitude change.
The old Bell two bladed main rotor system was known as a semi-rigid head (U.S.) or semi-teetering type (UK, Europe).
Depending on type of heli and assuming a long enough hard surface, safe run-ons or rolling landings can be made at ground speeds as low as 35-40 knots, paricularly if you have a decent wind from about the 10 o' clock direction (for CCW MRH) or from around the 2 o' clock direction if you prefer to fly French types (opposite turning MRH).
This really doesn't belong here. Maybe a mod could consider moving these rotary type posts?
But what I always thought counter-rotating propellers, as mkloby seems to be saying too, is when you have 2 propellers on 2 separate engines rotating in opposite directions, not a single propeller rotating the opposite from normal.
Wikipedia says likewise too: Counter-rotating propellers - Wikipedia, the free encyclopedia
Thus the XP-38 hat counter-rotating props rotating inward from the top (left-prop CW, right-prop CCW when viewed from behind/from the cockpit) while the production models used the opposite rotation with both outwardly rotating from the top. (which as previously stated was to improve air-flow and platform stability)
Ergo, the Wright flyer also used counter-rotating propellers.
What was the rationale that the propellers of P-38s rotate outwards had been a long unanswered question of my own.
If it was to make the control easier on a twin engine aircraft, the propellers should rotate inwards to bring the thrust line inwards and closer each other for the less effect of the thrust difference if one engine got troubled.
Only the reasonable explanation I got so far was that it makes the airflow over the wings stable from one of the present operator of a P-38 but was not in detail and I am not fully satisfied with that.