Robinson helicopters added to safety watchlist
will act in the same way - pitch down for a descent, pitch up for a climb.
Otherwise - what he said.
AOTW - yes, exactly what I was saying only better explained
Birdy2 - I suppose the teetering angle will change as the disc flaps up/down at the front but raising and lowering the lever should also change the coning angle.
Birdy2 - I suppose the teetering angle will change as the disc flaps up/down at the front but raising and lowering the lever should also change the coning angle.
"Once the rate of climb or descent builds up, then the effect of aerodynamic surfaces behind the center of gravity (e.g. stab / elevator, and tail boom itself) will act in the same way - pitch down for a descent, pitch up for a climb."
The writing leaves the impression that it takes time ( I.e., getting to a new steady state condition ) for the aerodynamics to take effect. But in fact the aerodynamics take effect as soon as the collective moves, since the angle of attack on the tail, be it fixed or a FBW stabilator, changes immediately. Sorry for proposing an example that is hard for the posters to replicate, but if you take a machine like the S-70, get it to 150, and then do a series of collective inputs, up/down, various increments and rates , stabilator active and stabilator fixed ( electronics OFF ) you'd see the effect is immediate. Don't mean to over react and I accept what I think was the meaning of your statement, and am sort of fencing with the verbiage.
The writing leaves the impression that it takes time ( I.e., getting to a new steady state condition ) for the aerodynamics to take effect. But in fact the aerodynamics take effect as soon as the collective moves, since the angle of attack on the tail, be it fixed or a FBW stabilator, changes immediately. Sorry for proposing an example that is hard for the posters to replicate, but if you take a machine like the S-70, get it to 150, and then do a series of collective inputs, up/down, various increments and rates , stabilator active and stabilator fixed ( electronics OFF ) you'd see the effect is immediate. Don't mean to over react and I accept what I think was the meaning of your statement, and am sort of fencing with the verbiage.
John, that's the problem with generalised statements regarding helicopters - there is always one which doesn't follow the norm and something with a variable stabilator will inevitably behave differently to something with a simple fixed stab.
It's worth highlighting that designers make all sorts of adjustments to their control rigging to overcome these basic aerodynamic effects using mechanical (mixing unit) or electrical (AP computer) inputs.
Sikorsky made the starboard lateral control run slightly longer (using the mixing unit) to help compensate for tail rotor drift and roll on the Wessex and Sea King and the Lynx has a very strong collective to fore and aft pitch interlink to counter the 'flapback' effect of raising and lowering the collective.
It's worth highlighting that designers make all sorts of adjustments to their control rigging to overcome these basic aerodynamic effects using mechanical (mixing unit) or electrical (AP computer) inputs.
Sikorsky made the starboard lateral control run slightly longer (using the mixing unit) to help compensate for tail rotor drift and roll on the Wessex and Sea King and the Lynx has a very strong collective to fore and aft pitch interlink to counter the 'flapback' effect of raising and lowering the collective.
Had a chance to fly the prototype Lynx with Roy Moxam in 1974, who briefed and demonstrated the collective G compensation sub-system. Worked fine. For a short while, we were planning on teaming with Westland, back when the USN idea on LAMPS was a small machine.
As we have discussed before John, the Collective Acceleration Control (CAC) activated at around 2G (we used to demonstrate it in a 60 deg AoB turn) and it took off collective pitch equivalent to about 15% Tq. You added more collective to maintain the turn but had to be careful to lower the lever again as you rolled out and reduced the G loading or you could overtorque.
I was told by the old and bold that it was designed in to the aircraft to try and reduce the severity of a pitch lane runaway.
I was told by the old and bold that it was designed in to the aircraft to try and reduce the severity of a pitch lane runaway.
That was awhile ago, Crab, but my dim recollection was that it was intended to soften the ride in turbulent air. Sort of a rigid rotor electronic version of an articulated rotor head delta three hinge. Same idea anyway.
Last edited by JohnDixson; 21st Nov 2016 at 21:29. Reason: Typo
Seem to recall flying the Huey on fixed floats when empty (aft CoG) the Vne was limited to 80 knots so as to be able to control the pitch up if Mr. Lycoming decided to take the day off. At 100 knots, the normal Vne, the cyclic was buried in the instrument panel in such conditions. Memory is decades old, so details may be a little off.
That might have been an additional benefit John but you would have to be in some serious turbulence to experience 2 G. I have had the CAC activate when mountain flying in very strong winds but that was in fairly extreme conditions.
One problem with the CAC was that it could runaway itself and they had to add a CAC cutout to the cyclic. The problem was to do with a 'wiper' style electrical contact for collective position that could be dislodged; I had this happen with a student conducting an AFCS out landing - all hell broke loose as we touched down (firmly but not hard) with severe vertical oscillations until the CAC cutout was pressed.
The G-meter on the aircraft registered +3.5G and -1.5G so I shut it down and it went home on a truck.
One problem with the CAC was that it could runaway itself and they had to add a CAC cutout to the cyclic. The problem was to do with a 'wiper' style electrical contact for collective position that could be dislodged; I had this happen with a student conducting an AFCS out landing - all hell broke loose as we touched down (firmly but not hard) with severe vertical oscillations until the CAC cutout was pressed.
The G-meter on the aircraft registered +3.5G and -1.5G so I shut it down and it went home on a truck.
Memory is decades old, so details may be a little off.
The writing leaves the impression that it takes time ( I.e., getting to a new steady state condition ) for the aerodynamics to take effect.
Join Date: Mar 2006
Location: uk
Posts: 144
Likes: 0
Received 0 Likes
on
0 Posts
Great engineering knowledge by all but NO pointers as to why these Robbos are
disentegrating in straight and level flight even when flown by very experienced pilots.
Hence their inclusion in the "watch" list.-- never again sit in one .
disentegrating in straight and level flight even when flown by very experienced pilots.
Hence their inclusion in the "watch" list.-- never again sit in one .
Join Date: Mar 2006
Location: uk
Posts: 144
Likes: 0
Received 0 Likes
on
0 Posts
Robinson now has the problem solved. Read their safety letter of 18th November.!!
Just slow down, do not speak to your passengers, dont change any radio frequencies
and everything will be ok.
Laughable if it wasnt such a serious issue.
Just slow down, do not speak to your passengers, dont change any radio frequencies
and everything will be ok.
Laughable if it wasnt such a serious issue.
Don't fly fast - don't overcontrol in turbulence - maybe just don't fly their helicopters
If it is an issue of division of attention when talking to pax that might distract the pilot from accurately and smoothly flying the aircraft - then surely the same must go for speaking on the radio, just as much of a drain on the brain. So, another don't for the list when flying a Robbie
Join Date: Mar 2006
Location: uk
Posts: 144
Likes: 0
Received 0 Likes
on
0 Posts
H500. Yes, in the 500 you can talk to your passengers if you so wish
but in a Robbo talking to them is simply too dangerous. It could result
in the machine falling apart.!
but in a Robbo talking to them is simply too dangerous. It could result
in the machine falling apart.!
Last edited by claudia; 24th Dec 2016 at 16:50.
"Robinson seem to assert this 'risk' is because a passenger is on board and not in any way associated with a design fault of the helicopter."
Robinson helicopters make up 35 per cent of the New Zealand fleet but 49 per cent of accidents, 64 per cent of fatal crashes and all seven fatal mast-bump accidents.
The company has blamed many accidents on poor pilot training, while critics have contended the helicopter has a design flaw.
Robinson helicopters make up 35 per cent of the New Zealand fleet but 49 per cent of accidents, 64 per cent of fatal crashes and all seven fatal mast-bump accidents.
The company has blamed many accidents on poor pilot training, while critics have contended the helicopter has a design flaw.
Vindicated - all those who believe Robbo's are death traps, even in the right hands.
The DoC in NZ have now permanently suspended the use of Robbo's going fwd. What more of an indictment could you have?
Now the Robbo company are "insinuating" that even distracting a pilot during their normal duties, might be enough to push the robbo closer or even into it's notorious mast bumping limits.
When will people wake up to the fact that cheap isn't always cheerful!
The DoC in NZ have now permanently suspended the use of Robbo's going fwd. What more of an indictment could you have?
Now the Robbo company are "insinuating" that even distracting a pilot during their normal duties, might be enough to push the robbo closer or even into it's notorious mast bumping limits.
When will people wake up to the fact that cheap isn't always cheerful!