Which helicopter has the most peculiar flight characteristics?
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Which helicopter has the most peculiar flight characteristics?
I can only speak from the perspective of piloting an R22, but i like to discuss and understand the handling quirks of more expensive to operate machinery. I'd like this thread to try to capture as many quirks of various machines as possible.
To start things off: for me the biggest quirk of the R22 is the need for the lateral cyclic bungee. This is required to trim the cyclic for inflow roll, but is often not taken back off when you return to the hover. This quirk means that hovering can require more intense concentration on ref points, as the helicopter is continuously suggesting you put in a port roll to cancel the force. R44 pilots, with their exotic hydraulics don't have this.
Any other quirks y'awl would like to share?
To start things off: for me the biggest quirk of the R22 is the need for the lateral cyclic bungee. This is required to trim the cyclic for inflow roll, but is often not taken back off when you return to the hover. This quirk means that hovering can require more intense concentration on ref points, as the helicopter is continuously suggesting you put in a port roll to cancel the force. R44 pilots, with their exotic hydraulics don't have this.
Any other quirks y'awl would like to share?
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Have you considered lateral drift caused by the tail rotor thrust?
On an R-22 /R-44 the rotor mast is fitted at an angle to compensate for the lateral drift...(cheap solution but requires more power)
In more expensive machines I believe the actual swashplate linkages and rotor system are designed to compensate for the drift...(Expensive solution but requires less power)
On an R-22 /R-44 the rotor mast is fitted at an angle to compensate for the lateral drift...(cheap solution but requires more power)
In more expensive machines I believe the actual swashplate linkages and rotor system are designed to compensate for the drift...(Expensive solution but requires less power)
The Hiller control system - a lot more control lag than anything else I've flown.
Felt pretty strange for the first few minutes until my brain got in sync with it on that first flight, then a non-issue - used to swap between a Hiller 12 & Bell 47 pretty often.
Felt pretty strange for the first few minutes until my brain got in sync with it on that first flight, then a non-issue - used to swap between a Hiller 12 & Bell 47 pretty often.
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This is spot on what i am after - thanks guys!
I'm trying to build a picture of the sorts of quirks pilots have to compensate for. This gives me an idea of what control systems need.
Another good one is Sasless comment's about operating the Chinook at Maximum Possible Weight, and having to operate rotor thrust close to where stall would pull down Nr.
The other one i have read about is Shawn Coyle commenting on torque limiters forcing rotors into a less efficient Nr, just when you need them to be efficient.
Brett, how did you compensate for the Hiller system? Did you just lower your input frequency, or were you actually trying to anticipate the machine (like a fast roll).
I'm trying to build a picture of the sorts of quirks pilots have to compensate for. This gives me an idea of what control systems need.
Another good one is Sasless comment's about operating the Chinook at Maximum Possible Weight, and having to operate rotor thrust close to where stall would pull down Nr.
The other one i have read about is Shawn Coyle commenting on torque limiters forcing rotors into a less efficient Nr, just when you need them to be efficient.
Brett, how did you compensate for the Hiller system? Did you just lower your input frequency, or were you actually trying to anticipate the machine (like a fast roll).
Nothing conscious - at first I'd make a "normal" cyclic correction, then when nothing happened right away I'd add a bit more & then end up overcontrolling. Typical PIO...and to add to the mix, the Hiller 12 had about half the throttle travel of a Bell 47.
The first few minutes were a lot like learning to hover again - I had about 150 hours TT, mostly in Bell 47's & R22's. But once it clicked, it was just like anything else.
The first few minutes were a lot like learning to hover again - I had about 150 hours TT, mostly in Bell 47's & R22's. But once it clicked, it was just like anything else.
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Bell 412 with engine governors that are not intended for aggressive flight. When you put in a pitch or roll input, you have to anticipate collective changes to prevent an overtorque.
Any tandem rotor helicopter, the lateral-directional stability (without augmentation) is just not intuitive. Multiple pedal inputs to maintain coordinated flight on roll entry, roll capture, and then maintaining in a turn. Repeat when exiting. H46 with an early SAS still required a lot of pilot input to help with this, but I didn't notice this too much on the British Chinooks.
Mi-2 with extremely high control forces required leading cyclic with trim, unless you are transformer-strong.
OH-6 in an entry to an autorotation required moving my elbows in unusual manners due to the large control inputs and restrictive cockpit space.
Those are some of the highlights I can think of. Remember that what is a peculiarity in one role, may be completely unnoticed in another, or even completely unacceptable.
Matthew.
Any tandem rotor helicopter, the lateral-directional stability (without augmentation) is just not intuitive. Multiple pedal inputs to maintain coordinated flight on roll entry, roll capture, and then maintaining in a turn. Repeat when exiting. H46 with an early SAS still required a lot of pilot input to help with this, but I didn't notice this too much on the British Chinooks.
Mi-2 with extremely high control forces required leading cyclic with trim, unless you are transformer-strong.
OH-6 in an entry to an autorotation required moving my elbows in unusual manners due to the large control inputs and restrictive cockpit space.
Those are some of the highlights I can think of. Remember that what is a peculiarity in one role, may be completely unnoticed in another, or even completely unacceptable.
Matthew.
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Some folks have all the fun! With only about 100TT in helos, mostly in an Enstrom 480B (and some in R22/R44/206), all I can say is that the E480 seems entirely devoid of unusual flight characteristics. Probably way too tame for most here, but I am impressed with how well the engineers did in designing out or toning down many of the "gotchas" forund in some other makes/models.
RB
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Oh, and another one. Not strictly a 'flight' characteristic, but can catch you out.
In a Schweizer 300, engine started, but clutch not engaged, take your hand off the lever (to put headset on for instance)...and the lever friction is mistakenly off.... the lever shoots up to full pitch and overspeeds the engine.
In a Schweizer 300, engine started, but clutch not engaged, take your hand off the lever (to put headset on for instance)...and the lever friction is mistakenly off.... the lever shoots up to full pitch and overspeeds the engine.
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R22 at 80kt cruise/20inch MP wants to climb and must hold forward cyclic.A mild pain to constantly hold forward cyclic against this tendency and no way to trim it out.
JR
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I always thought that was a fault with you, not the Puma 
CG
Did you go to the reunion? I couldn't
Puma HC1's roll/yaw divergence is always good for a laugh.
CG
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I just remember a strange flight characteristic when doing a return to target, and if you didn't reduce power in the verticle climb the helo would actually climb vertical while starting to fly backwards. But that was in a different platform.......alot of power. Then you get used to it. -64
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Wow this is great, guys! Too many to respond to all, but all read and appreciated.
The more i understand about the constraints of helicopter design, the more i am beginning to realise the benefit of various electronic augmentation systems. These vary from sorting out the engine limits when a Cat A machine goes OEI (including 30 sec power), to overcoming stability problems which aerodynamics alone can't solve (like Chinook yaw). In future this will also likely extend to modifying all control inputs to make machine do what is intended rather than demanded (like optimise collective for engine power available and rotor Nr, or feedforwards of cyclic to anticipate manouvre rate).
Howabout for the various roles that a helicopter is asked to do? Operationg below HV curve or long lining? What aspects of flying the machine are hardest to train for?
The more i understand about the constraints of helicopter design, the more i am beginning to realise the benefit of various electronic augmentation systems. These vary from sorting out the engine limits when a Cat A machine goes OEI (including 30 sec power), to overcoming stability problems which aerodynamics alone can't solve (like Chinook yaw). In future this will also likely extend to modifying all control inputs to make machine do what is intended rather than demanded (like optimise collective for engine power available and rotor Nr, or feedforwards of cyclic to anticipate manouvre rate).
Howabout for the various roles that a helicopter is asked to do? Operationg below HV curve or long lining? What aspects of flying the machine are hardest to train for?
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This is really an interesting thread.
Some philosophical points - there is no perfect design, nor a perfect operator.
Pilots end up compensating for the shortcomings of a machine in order to carry out the necessary task. How much you have to compensate depends on the machine.
A great example is trying to hover very close to an object - say trying to put workers onto the top of a power pylon. It is very easy to do in some machines, as the controls and rotor head together make the machine very responsive immediately. Same task in a different helicopter - say with an underslung rotor head - is nearly impossible to do. (Some pilots can do it, but I certainly can't).
Those who can do it are compensating very well. But many can't compensate that well.
Perhaps another thing to look at are - what are the strangest types of flying that you've heard of being done in a helicopter? For me, the two most interesting from a flying qualities point of view are:
a) trying to hold a mirrored box on the front of the the helicopter directly over a vertically pointed laser beam while climbing to a thousand feet AGL so that surveyors miles away can take a shot at said box on the front to extend their survey points. Legend has it that only one in a hundred pilots could it.
b) towing a mine-sweeping sled at a constant groundspeed and over desired track. Turns were led with opposite pedal, if memory serves me right.
In both cases, pilots were working like mad to complete the task.
But, please more things we find unusual about these machines. I'll see if I can explain some of them.
Some philosophical points - there is no perfect design, nor a perfect operator.
Pilots end up compensating for the shortcomings of a machine in order to carry out the necessary task. How much you have to compensate depends on the machine.
A great example is trying to hover very close to an object - say trying to put workers onto the top of a power pylon. It is very easy to do in some machines, as the controls and rotor head together make the machine very responsive immediately. Same task in a different helicopter - say with an underslung rotor head - is nearly impossible to do. (Some pilots can do it, but I certainly can't).
Those who can do it are compensating very well. But many can't compensate that well.
Perhaps another thing to look at are - what are the strangest types of flying that you've heard of being done in a helicopter? For me, the two most interesting from a flying qualities point of view are:
a) trying to hold a mirrored box on the front of the the helicopter directly over a vertically pointed laser beam while climbing to a thousand feet AGL so that surveyors miles away can take a shot at said box on the front to extend their survey points. Legend has it that only one in a hundred pilots could it.
b) towing a mine-sweeping sled at a constant groundspeed and over desired track. Turns were led with opposite pedal, if memory serves me right.
In both cases, pilots were working like mad to complete the task.
But, please more things we find unusual about these machines. I'll see if I can explain some of them.