High Hover
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High Hover
If a rotor system was devised that although slowing down the rate of cyclic responce, allowed safe controlled autos from a forty foot hover, do you think it would be a desirable feature?
Long stroke oleos with big wheels on (Wessex, Blackhawk) that won't make the auto easier but takes a lot of sting out of the landing!
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This situation needs a bit more detail before it can be answered - how or what is going to give the trade off of cyclic response to improved rotor energy?
Years ago Bell did a project with a Jet Ranger with increased inertia in the blades (quite a bit of increased weight). The result showed that for this machine, there was no HV curve- that is, no combination of airspeed and height that would prevent a safe landing. But this would only be over a suitable landing area, of course.
So what is the mechanism that is going to give us this increased benefit - need to know that before the question can be answered.
And for Part 29 helicopters (more than 7,000lbs) with more than 10 seats, the HV curve is a limitation, so unless you can eliminate the HV curve, you won't help those operators.
More info please!!!
Years ago Bell did a project with a Jet Ranger with increased inertia in the blades (quite a bit of increased weight). The result showed that for this machine, there was no HV curve- that is, no combination of airspeed and height that would prevent a safe landing. But this would only be over a suitable landing area, of course.
So what is the mechanism that is going to give us this increased benefit - need to know that before the question can be answered.
And for Part 29 helicopters (more than 7,000lbs) with more than 10 seats, the HV curve is a limitation, so unless you can eliminate the HV curve, you won't help those operators.
More info please!!!
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I don't understand this thread at all so I thought I should definately add my 2 cents worth.
There is a company here in Aus that specializes in power line work and so operate for very long periods in the dead mans curve(titty graph... for the mustering pilots). They practice hovering auto's from 50 feet in 500's as part of their regular check and training programme
There is a company here in Aus that specializes in power line work and so operate for very long periods in the dead mans curve(titty graph... for the mustering pilots). They practice hovering auto's from 50 feet in 500's as part of their regular check and training programme
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High Hover
Right. Let me run through it again. You are in stationary hover at forty feet or thereabouts. You engine or engines, or turbines quit on you. Would it be reasonable to assume that one has a definate problem. The remarks that no one hovers at this height seem incorrect to me, look at any search and rescue, air ambulance or Irak footage. OK now if in this situation there was enough stored energy in your rotors to get you down to earth in a controlled manner, at the overall cost of a slightly slower responce to general cyclic inputs, would you consider this tradeoff worthwhile. I ask this question not to start a rediculous thread which obviously delights some of the piss takers, and I genuinely cannot describe at this date, a theory as to how it can be achieved. I ask the question, seeking genuine comments from professional pilots
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"You are in stationary hover at forty feet or thereabouts. You engine or engines, or turbines quit on you."
Statistically unlikely although I check my autopilot at this height so pheasable. If luck is against you and you do not have single engine performance, a bent helicopter is likely to be the worst scenario. I for one do not care to much about bent aeroplanes that people walk away from. There is obviously an agenda here and the originator is going to have to be a little more up front regarding where he is coming from IMHO.
Statistically unlikely although I check my autopilot at this height so pheasable. If luck is against you and you do not have single engine performance, a bent helicopter is likely to be the worst scenario. I for one do not care to much about bent aeroplanes that people walk away from. There is obviously an agenda here and the originator is going to have to be a little more up front regarding where he is coming from IMHO.
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Alot of Helipilots get hung up on the (Titty) HV Chart. Keep in mind that these charts are advisory (not Cold Limitations).
The HV chart has some fluidity to it's interpretation. Wind velocity
directly reduces the curve apex. Right turn, left turn, pitch up or down also has an effect (and any combination) Then there is the design fudge factor, certified authority factor etc. I have conducted throttle roll offs at 50' in B206's and UH-1's. The amount of kinetic energy stored is directly proportional to the reaction of the pilot's control input in such a situation. I'm sure all mono heli's don't react the same, and I have reservations about the R-22 models as well as one or two low inertia systems.
But remember when inside the Deadmans curve, be prepared to snap the collective down controlled and firmly....initially!!!!!!
The HV chart has some fluidity to it's interpretation. Wind velocity
directly reduces the curve apex. Right turn, left turn, pitch up or down also has an effect (and any combination) Then there is the design fudge factor, certified authority factor etc. I have conducted throttle roll offs at 50' in B206's and UH-1's. The amount of kinetic energy stored is directly proportional to the reaction of the pilot's control input in such a situation. I'm sure all mono heli's don't react the same, and I have reservations about the R-22 models as well as one or two low inertia systems.
But remember when inside the Deadmans curve, be prepared to snap the collective down controlled and firmly....initially!!!!!!
Helipolarbear:
Umm. Well... Actually, there are many helicopters in which the H-V chart *is* in the Limitations Section and therefore is more than just "advisory" in nature (Check the AS-350 AFM for one.)
Umm. Well... You know, the H-V chart is marked with units of (if I recall correctly) "height" and "velocity." Velocity is measured as airspeed, which is quite independant of wind. Wind does not figure into the equation, nor does it have any effect on the shape of the shaded area.
Any pilot who "simulates" an engine failure in a BH-206 by snapping the throttle off is deluding himself if he thinks this is an accurate representation of what will happen if the engine quits for real. Having said that, we can all agree that merely operating in the shaded area is no guarantee of a crash. For every kilo you are under MGW is an advantage in your favor. For every millivanillisecond your reaction time is better than the test pilot's is an advantage in your favor.
Back to Bugdevheli's original question- - -
Let us allow that the only helis this really applies to are single-engine ships. And so we must ask: Is the shaded area of the H-V chart that much of an impediment? Is it that hard to avoid? I think not. Use the right tool for the job...in other words, don't be using an R-22 for OGE, inside-the-shaded-area hovering. If you must do such work and cannot afford a twin, use a lightly-loaded 206!
Would I trade maneuverability for inertia? Not really. Remember, rotor intertia would not necessarily mean a concomitant increase in stability. A slow-reacting rotor could be a real detriment - - like hovering in close quarters on a gusty day, say - - or trying to put the ship on a dolly on that same gusty day. No sir, give me quick control response any day.
Alot of Helipilots get hung up on the (Titty) HV Chart. Keep in mind that these charts are advisory (not Cold Limitations).
The HV chart has some fluidity to it's interpretation. Wind velocity directly reduces the curve apex.
Right turn, left turn, pitch up or down also has an effect (and any combination) Then there is the design fudge factor, certified authority factor etc. I have conducted throttle roll offs at 50' in B206's and UH-1's. The amount of kinetic energy stored is directly proportional to the reaction of the pilot's control input in such a situation. I'm sure all mono heli's don't react the same, and I have reservations about the R-22 models as well as one or two low inertia systems.
But remember when inside the Deadmans curve, be prepared to snap the collective down controlled and firmly....initially!!!!!!
But remember when inside the Deadmans curve, be prepared to snap the collective down controlled and firmly....initially!!!!!!
Back to Bugdevheli's original question- - -
Let us allow that the only helis this really applies to are single-engine ships. And so we must ask: Is the shaded area of the H-V chart that much of an impediment? Is it that hard to avoid? I think not. Use the right tool for the job...in other words, don't be using an R-22 for OGE, inside-the-shaded-area hovering. If you must do such work and cannot afford a twin, use a lightly-loaded 206!
Would I trade maneuverability for inertia? Not really. Remember, rotor intertia would not necessarily mean a concomitant increase in stability. A slow-reacting rotor could be a real detriment - - like hovering in close quarters on a gusty day, say - - or trying to put the ship on a dolly on that same gusty day. No sir, give me quick control response any day.
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I recall that the HV curve is part of the certification process, in the US, during which test pilots from the manufacturer and the FAA fly the helicopter. They come up with the absolute limits of the HV diagram (or any other limitation) and then these limits are expanded to where the "average" pilot should be able to perform whatever action is needed to land the helicopter provided a satisfactory landing area is available.
As for being able to perform auto's from outside the HV diagram many helicopters will do depending on many factors. I knew a guy that lost his engine in a Huskie just after beginning to pull pitch off a log landing. He was able to move away from the landing and maneuver between two trees and land the helicopter with no damage from a 150' hover.
As for being able to perform auto's from outside the HV diagram many helicopters will do depending on many factors. I knew a guy that lost his engine in a Huskie just after beginning to pull pitch off a log landing. He was able to move away from the landing and maneuver between two trees and land the helicopter with no damage from a 150' hover.
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Pprune Fan #1: As wind is not a factor with the HV chart by your reckoning....I suggest that YOU use the HV chart as a limitation at all times! And whatever you do...count your units!!!
If someone were able to produce a Very Light Helicopter which had the following attributes ; Deisel engine. One piece composite airfame/body. Rotor system that would permit engine off landings from 30foot hover. Running costs of £20/hr. The limitations being, Single place, Max operating height 40 feet. Limited range. Would there be a market for such a machine?
Why are you so attached to putting a ceiling on this machine. We want to fly, not hug the ground.
Mind you it might go down well with the swamp buggy fraternity...check their forum out
Tightgit
Didn't somebody already invent a helicopter with an ability to auto from 40 ft but with the penalty of a low cyclic response...and wasn't it called a Huey?
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High Hover
Still a dreamin TC! . Thanks for the replies so far. Very informative. Be nice to hear from someone who has experienced this situation in a single engine two bladed machine.
. Thanks for the replies so far. Very informative. Be nice to hear from someone who has experienced this situation in a single engine two bladed machine.
Helipolarbear:
Well I guess you told me!
...I'm not exactly sure what you've told me, but you did it.
I will endeavor to learn just how wind modifies the shape of the shaded-area of the H-V chart, and I will use said chart as a limitation in aircraft where that applies.
Pprune Fan #1: As wind is not a factor with the HV chart by your reckoning....I suggest that YOU use the HV chart as a limitation at all times! And whatever you do...count your units!!!
...I'm not exactly sure what you've told me, but you did it.
I will endeavor to learn just how wind modifies the shape of the shaded-area of the H-V chart, and I will use said chart as a limitation in aircraft where that applies.
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The UltraSport 254 has a disk loading of 1.52 lbs/sq-ft. and a descent rate of 15 ft/sec. It is also claimed that the Ultrasport has enough inertia to autorotate to the ground then lift off and re-land.