.....Not so.
....also 600,000lb/ft from a tail rotor? Not so.
But off topic. Sorry to dump this on the thread.
Why propellers of P-38 Lightning rotate outwards?
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.....Not so.
....also 600,000lb/ft from a tail rotor? Not so.
But off topic. Sorry to dump this on the thread.
drgondog
Major
Main rotor. Unrestrained when tail rotor lost. Ship rotates violently in the opposite direction from main rotor.
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.
Cheers,
Wes
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.
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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
I could not tell you if tail rotor loss was recoverable in a 206 or 407.
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.)
Cheers,
Wes
drgondog
Major
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.
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, particularly 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?
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Thats true. Now that I think about it, we had a 212 lose its TR in the gulf and return for a run on as well. Well when I say we, I don't mean we, it was well before I started working there. I only read the report.
And I agree. I will move them all when I am not on my phone.
GrauGeist
Generalfeldmarschall zur Luftschiff Abteilung
The reason Lockheed went with the "outer" rotation versus "inner" rotation, was due to lift issues.
Inner rotation was robbing the necessary lift needed from the inner mainwing, reversing the rotation corrected that issue.
Inner rotation was robbing the necessary lift needed from the inner mainwing, reversing the rotation corrected that issue.
I seem to recall an article that was authored by Corky Meyer, who recalled that the XP-38 had an overly long take off run, until they discovered that the original prop rotation was creating enough turbulence that the wing center section was not producing lift. The engine direction swap solved the problem, as has been said.
haitipro
Recruit
I was lucky enough to fly a P-38 and, ignoring all of the technical possibilities, it made the aircraft a "torque free" handling situation, unlike other twins I have flown, including the Mosquito, which required your attention. The P-38 had zero torque reaction when rapid, full-power was applied on take-off.
Regarding propeller direction and its effect, we can look at the Corsair. We'll confine ourselves to the carrier approach and go around regime. The prop's right hand rotation swirled the air (propwash) around the fuselage to the right, with the prop, causing the inboard left wing to have a higher relative Angle of Attack than the inboard right wing. If the aircraft got "slow enough" and power was increased "high enough" the relative AoA on the left inboard wing (upward blade) would exceed the wing's critical AoA and stall while the right inboard wing (downward blade) would be stall "resistant" due to its much lower relative AoA and, with the left inboard wing stall being pulled rapidly outboard by the now (safe to assume) down left aileron the plane rolls left. This was "fixed" by the right hand wing's subsequent stall strip mounted outboard of the propwash to induce a matching stall on the right side. (This hurt turn performance, however, but who cared?)
This same effect is what they were alleviating on the P-38. With inboard turning props (XP-38) you have better single engine performance particularly at higher AoA's due to a resulting thrustline (P factor) closer to the aircraft centerline (less corrective rudder) BUT at higher power the wing outboard of the boom (upward moving prop blade) is where your stall will begin (the relative AoA thing). If you are engaged in a tight turn at high power you could easily (if you're fitter than I am) start riding the edge of the stall. As the stall starts/stops/can't decide the effect on the plane is rather dramatic as the wing is losing-a-smidge/gaining-it-back lift outboard of one/both/alternately the booms requiring rapid and substantial aileron correction to maintain roll angle. With outboard turning props this higher power, higher AoA stall effect is much less as the fluctuating lift loss is inboard of the booms much nearer the centerline.
Sssooooo ... Lockheed went with two "critical" engines sacrificing improved single engine performance for improved both-engine, or we should say, combat, performance.
This same effect is what they were alleviating on the P-38. With inboard turning props (XP-38) you have better single engine performance particularly at higher AoA's due to a resulting thrustline (P factor) closer to the aircraft centerline (less corrective rudder) BUT at higher power the wing outboard of the boom (upward moving prop blade) is where your stall will begin (the relative AoA thing). If you are engaged in a tight turn at high power you could easily (if you're fitter than I am) start riding the edge of the stall. As the stall starts/stops/can't decide the effect on the plane is rather dramatic as the wing is losing-a-smidge/gaining-it-back lift outboard of one/both/alternately the booms requiring rapid and substantial aileron correction to maintain roll angle. With outboard turning props this higher power, higher AoA stall effect is much less as the fluctuating lift loss is inboard of the booms much nearer the centerline.
Sssooooo ... Lockheed went with two "critical" engines sacrificing improved single engine performance for improved both-engine, or we should say, combat, performance.
