Is a second or so enough?
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Is a second or so enough?
Having worked on a prototype tandem machine it becomes apparent that weight distribution is a problem. To accomodate a variety of front pilot weights on what is to be a light helicopter would indicate that some form of sliding ballast is required, and we cant carry any excess weight!. Instruments and long control runs again push up the weight. Because of the increased body area necessary to cover the two pilots when sitting tandem the benifits, whatever they may be, seem to be cancelled out by the additional bodyweight. If the rear seat is to be situated directly beneath the mast in order that the rear pilot does not afect the c of g, the engine has to go that little further back which again compounds the balance problem. What are the advantages of a tandem seating arrangement?.
The above post should be under lets build a helicopter! can somebody move it please?
The above post should be under lets build a helicopter! can somebody move it please?
I'll concur with Pat on this one - I had constant attitude autos at 40 knots demoed to about 15 - 20 feet at night (when the grass comes into view).
Logic was at night you didn't want a flare because you couldn't then judge the last bit to end up level.
During the day, I'll take a standard auto with flare to get RoD and speed to an absolute minimum. And if I'm honest, I'd rather be in a Jettie or R44 when it does happen . . .
Logic was at night you didn't want a flare because you couldn't then judge the last bit to end up level.
During the day, I'll take a standard auto with flare to get RoD and speed to an absolute minimum. And if I'm honest, I'd rather be in a Jettie or R44 when it does happen . . .
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Hughes 500
I have a total of about 5 hours in Frank's machines, and none of it instructional, so I'm not in any position to anwer your question. That's why I asked if anyone had any experience doing it.
My experience on the Bell 206 series has shown me that constant attitude autos are pretty straightforward, but most people think you're going to die if you even try.
Hence the question - has anyone tried them to the ground in an R-22? If we haven't then we may be condemning a perfectly good technique for no good reason.
And God help me if I ever become a politician....
I have a total of about 5 hours in Frank's machines, and none of it instructional, so I'm not in any position to anwer your question. That's why I asked if anyone had any experience doing it.
My experience on the Bell 206 series has shown me that constant attitude autos are pretty straightforward, but most people think you're going to die if you even try.
Hence the question - has anyone tried them to the ground in an R-22? If we haven't then we may be condemning a perfectly good technique for no good reason.
And God help me if I ever become a politician....
Pat
I did read it, you are assuming that you would do a 60 kt forward touchdown. If you fare off the speed you can put it straight down with no forward speed and without breaking anything. Best of luck if you bang an R22 in and rely on the seat structure and skid gear at 20 mph to zero . Before you do check to make sure no one has left anything under the seat like fuel tank dipstick, unless you like being pulled through with one !!
Now at night like the rest of mil pilots we were taught constant attitude - follow the landing light down - see the blades of grass and pull lever. Works well in gazelle and 206. I think the chances of bending an R22 are high doing this !
I did read it, you are assuming that you would do a 60 kt forward touchdown. If you fare off the speed you can put it straight down with no forward speed and without breaking anything. Best of luck if you bang an R22 in and rely on the seat structure and skid gear at 20 mph to zero . Before you do check to make sure no one has left anything under the seat like fuel tank dipstick, unless you like being pulled through with one !!
Now at night like the rest of mil pilots we were taught constant attitude - follow the landing light down - see the blades of grass and pull lever. Works well in gazelle and 206. I think the chances of bending an R22 are high doing this !
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I have been shown a couple while on the controls, I know its not the same as doing them, but Ill give a breif run through.
It was a simulation type run, emergency landing to small area, the idea being you didnt want to loose sight of your landing area by doing S turns.
60knts, 1500ft, reducing speed to 35-40knts IAS. Maintaining RRPM top of green. You really come down very steeply. First time feels like youre droppng vertically.
I would like to say the alt that pitch was pulled, Im guessing that it came on at about 60-75ft AGL, but Im really not sure, it all happens pretty quick. Arresting ROD, with a extra pull at teh bottom to cusion.
The instructor showed me 2 to ground. I stayed on the controls for both, but I wouldnt like to try one myself, not yet anyway.
I must say the first one really scared the c**p out of me. It feels very different to a "standard auto", especially during the decent. Its at the bottom where it all starts to become very quick.
Probably what makes it so harrowing is seeing the sirspeed drop below 60knts. You have drilled into you that 60knts is life in the robbie, so doing something different can be pretty unnerving at first.
I think that the reason the 60knt flare auto is the recommended is that if a low time pilot has an engine failure, establishes autorotation, and performs some sort of flare at teh bottom, then more than likely he will walk away, even if the machine is destroyed. Im not so sure that low time pilot in a constant speed auto, screwing it up at the bottom would be so lucky.
However all that paled in comparison to the backwards auto. Im convinced that that is not a natural manouver.
It was a simulation type run, emergency landing to small area, the idea being you didnt want to loose sight of your landing area by doing S turns.
60knts, 1500ft, reducing speed to 35-40knts IAS. Maintaining RRPM top of green. You really come down very steeply. First time feels like youre droppng vertically.
I would like to say the alt that pitch was pulled, Im guessing that it came on at about 60-75ft AGL, but Im really not sure, it all happens pretty quick. Arresting ROD, with a extra pull at teh bottom to cusion.
The instructor showed me 2 to ground. I stayed on the controls for both, but I wouldnt like to try one myself, not yet anyway.
I must say the first one really scared the c**p out of me. It feels very different to a "standard auto", especially during the decent. Its at the bottom where it all starts to become very quick.
Probably what makes it so harrowing is seeing the sirspeed drop below 60knts. You have drilled into you that 60knts is life in the robbie, so doing something different can be pretty unnerving at first.
I think that the reason the 60knt flare auto is the recommended is that if a low time pilot has an engine failure, establishes autorotation, and performs some sort of flare at teh bottom, then more than likely he will walk away, even if the machine is destroyed. Im not so sure that low time pilot in a constant speed auto, screwing it up at the bottom would be so lucky.
However all that paled in comparison to the backwards auto. Im convinced that that is not a natural manouver.
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So far, so good: but keep going . . .
No-flare autos are becoming more of an R22 possibility as we go along, thanks all. But I can't put together a complete lesson plan yet: Spaced, what happens with the 40k forward airspeed (assume zero wind if convenient). Is ALL the paltry MR inertia expended on arresting descent, with a high-speed run-on touchdown? Or does the pitch attitude increase along with collective so that some of the MR energy is expended to decelerate before impact with the pungee stakes?
For the theoreticians (you know who you are!): where does this exploration of the survival envelope fall in terms of minimum-power-required (?53k in R22 = Vy), OR best glide (perhaps irrelevant, but in the last few years R22's seem to be assigned 75k), OR optimum autorotation IAS (65k quoted by RHC, there seems to be no aerodynamic justification for this, just Tradition, the Force Majeur in rotary flight!).
Seems like the alert CFI/practical aerodynamicist ought to be able to cook up a coherent energy management scenario (Delta 3, Lu?). Us CFI's out here in the trenches need sensible explanations to pass on to students--something better than "it's always been done that way."
For the theoreticians (you know who you are!): where does this exploration of the survival envelope fall in terms of minimum-power-required (?53k in R22 = Vy), OR best glide (perhaps irrelevant, but in the last few years R22's seem to be assigned 75k), OR optimum autorotation IAS (65k quoted by RHC, there seems to be no aerodynamic justification for this, just Tradition, the Force Majeur in rotary flight!).
Seems like the alert CFI/practical aerodynamicist ought to be able to cook up a coherent energy management scenario (Delta 3, Lu?). Us CFI's out here in the trenches need sensible explanations to pass on to students--something better than "it's always been done that way."
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pa42,
The issue is one of energy management, and the problem is that you have barely enough when all is working right. Look at the Space Shuttle landing, and note that it floats for a solid 10 seconds dropping at about 2 ft/sec at impact. I wish my helos would float that long on residual energy!
The ability to coax a zero ROD/ zero forward speed landing out of your machine is best achieved at the recommended procedure in the manual. If you plotted the ROD and forward speed as the two contributors to the energy state, and valued each alike, you would find that most helos want to be descended in auto at the forward edge of their best rate of climb speed (Vy).
Try your helo and see. Just settle up in auto descent at the recommended auto speed, and note the ROD. Redo the trial but set 15 knots faster, and then again at 15 knots slower.
The idea of a constant attitude descent seems so cool, but is not the ideal way to dissipate the total kinetic energy of the machine. Holding some extra forward speed (while not increasing rate of descent) is a way to bank some cyclic flare that arrests rate of descent without relying on the rotor energy. Many helos I have flown can arrest the ROD without pulling collective pitch. This has distinct benefits in conserving the rotor rpm for the touchdown. For rotorcraft with low rotor inertia, I believe a flare type auto is the most desirable, by far, and the most likely to result in a successful auto.
Having done the S-76 autos for certification at the highest weights and at the highest altitudes, I strongly suggest that nobody try to invent their own procedure and ignore the flight manual. Strongly!
The issue is one of energy management, and the problem is that you have barely enough when all is working right. Look at the Space Shuttle landing, and note that it floats for a solid 10 seconds dropping at about 2 ft/sec at impact. I wish my helos would float that long on residual energy!
The ability to coax a zero ROD/ zero forward speed landing out of your machine is best achieved at the recommended procedure in the manual. If you plotted the ROD and forward speed as the two contributors to the energy state, and valued each alike, you would find that most helos want to be descended in auto at the forward edge of their best rate of climb speed (Vy).
Try your helo and see. Just settle up in auto descent at the recommended auto speed, and note the ROD. Redo the trial but set 15 knots faster, and then again at 15 knots slower.
The idea of a constant attitude descent seems so cool, but is not the ideal way to dissipate the total kinetic energy of the machine. Holding some extra forward speed (while not increasing rate of descent) is a way to bank some cyclic flare that arrests rate of descent without relying on the rotor energy. Many helos I have flown can arrest the ROD without pulling collective pitch. This has distinct benefits in conserving the rotor rpm for the touchdown. For rotorcraft with low rotor inertia, I believe a flare type auto is the most desirable, by far, and the most likely to result in a successful auto.
Having done the S-76 autos for certification at the highest weights and at the highest altitudes, I strongly suggest that nobody try to invent their own procedure and ignore the flight manual. Strongly!
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As a crumb counter, I know little about engineering but all the formulae I remember in colludge always seemed to have V squared when calculating energy.
Therefore, I am a big fan of not being short on airspeed.
Therefore, I am a big fan of not being short on airspeed.
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Please don't misunderstand my reasons for advocating the 'constant attitude' autorotation.
I fully agree with Nick and diethelm that airspeed is great, and that the V squared aspect is not well understood.
What I was trying to get across is that if you're going to teach a beginner something that is easy to do and has a good chance of survival, why not start with the constant attitude auto? Once proficient enough at that to survive when the unexpected happens, then start with the variations.
It has the advantage that in nearly all forward flight situations it would involve the helicopter being flared as part of the immediate actions following engine failure, which helps to build / maintain rotor RPM.
I fully agree with Nick and diethelm that airspeed is great, and that the V squared aspect is not well understood.
What I was trying to get across is that if you're going to teach a beginner something that is easy to do and has a good chance of survival, why not start with the constant attitude auto? Once proficient enough at that to survive when the unexpected happens, then start with the variations.
It has the advantage that in nearly all forward flight situations it would involve the helicopter being flared as part of the immediate actions following engine failure, which helps to build / maintain rotor RPM.
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Regarding whether a second or so is enough following engine failure, I was at a CAA safety evening last night where they touched on helicopter fatal accidents in the UK over the last eight years.
There were about 20, only one of which involved engine failure, and that resulted from neglect of carb heat.
Most of the remainder were bad attitude/poor decision-making. Loss of control in IMC. "Ran into high ground in IMC at night." In an R22, yet.
A second may or may not be enough in case of engine failure, but we can make decisions on whether or not to fly at our leisure.
There were about 20, only one of which involved engine failure, and that resulted from neglect of carb heat.
Most of the remainder were bad attitude/poor decision-making. Loss of control in IMC. "Ran into high ground in IMC at night." In an R22, yet.
A second may or may not be enough in case of engine failure, but we can make decisions on whether or not to fly at our leisure.
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Thank you, Pat!
I have prattled on about this, and now you have joined the Side of Reason.
The Lord gave us engine controls, and we put them to good use to practice engine failures and autorotations. We practice them enough to declare them to be the Prime Safety Concern. Now we fill pages and pages of threads about how many engines is enough, and how much performance we must have after an engine fails, and how few seconds we have to save ourselves from The Dreaded Engine Failure. Great Long Windy Discussions ensue.
Meanwhile, we run into hills, fly into bad weather with inappropriate instrumentation and hit trees and wires and things, and nobody ever asks "How do we stop this from happening?" Indeed.
thanks, Pat!
I have prattled on about this, and now you have joined the Side of Reason.
The Lord gave us engine controls, and we put them to good use to practice engine failures and autorotations. We practice them enough to declare them to be the Prime Safety Concern. Now we fill pages and pages of threads about how many engines is enough, and how much performance we must have after an engine fails, and how few seconds we have to save ourselves from The Dreaded Engine Failure. Great Long Windy Discussions ensue.
Meanwhile, we run into hills, fly into bad weather with inappropriate instrumentation and hit trees and wires and things, and nobody ever asks "How do we stop this from happening?" Indeed.
thanks, Pat!
Nick/Pat I would agree entirely, in 15 years of flying I have had one engine failure. In the UK the biggest problem is the double edged sword of satnav. Before it came about low time pilots would not go flying in bad / marginal weather as they were concerned about getting lost. Now I often hear weather is bad but we will go as we don't need to wory about getting lost. Yes the moving map is great, even better in bad weather when you have a topo one, but they succour you in to pushing the limits !
