Low level, high speed, single engine.
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Low level, high speed, single engine.
Hello all,
I've been pondering the following scenario.
Gazelle driver (could be anybody really), giving it max chat over ****** at their infamous 'map of the earth' (IIRC that's the correct phrase) altitude has some sort of engine issue.
Given Gazelle has a single engine, I presume that this sort of low-level activity has it's risks, but you're usually within the safe area of the HV diagram - correct?
Then; if you are at such a low level/high speed combination and the donk does give up the ghost is it just a case of managing the collective and flaring at the appropriate moment after a relatively short/quick auto, or even run-on landing.
Thanks all.
Mungs.
I've been pondering the following scenario.
Gazelle driver (could be anybody really), giving it max chat over ****** at their infamous 'map of the earth' (IIRC that's the correct phrase) altitude has some sort of engine issue.
Given Gazelle has a single engine, I presume that this sort of low-level activity has it's risks, but you're usually within the safe area of the HV diagram - correct?
Then; if you are at such a low level/high speed combination and the donk does give up the ghost is it just a case of managing the collective and flaring at the appropriate moment after a relatively short/quick auto, or even run-on landing.
Thanks all.
Mungs.
Last edited by Senior Pilot; 26th Nov 2008 at 21:01. Reason: de indentify the aircraft
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Nap of the Earth actually.
So you could convert the horizontal inertia into height by hauling back on the cyclic, keeping the collective up to counteract the Nr overspeed, then managing the speed and Nr as required to autorotate. This may give you enough height to do a turn or try to make a better area for landing.
You could also just do a nice long flare and accept where you are going. Manage the Nr accordingly.
Yes, they do train for this eventuality. Good fun too !!
Watch out for the high speed / low altitude section of the HV diagram, they are probably in it most of the time in this scenario.
So you could convert the horizontal inertia into height by hauling back on the cyclic, keeping the collective up to counteract the Nr overspeed, then managing the speed and Nr as required to autorotate. This may give you enough height to do a turn or try to make a better area for landing.
You could also just do a nice long flare and accept where you are going. Manage the Nr accordingly.
Yes, they do train for this eventuality. Good fun too !!
Watch out for the high speed / low altitude section of the HV diagram, they are probably in it most of the time in this scenario.
Just like "What Limits" said---depending upon how much inertia you have in the speed, you can flare, get altitude, and sometimes even turn. It was a required maneuver to be demonstrated on a FAR 137 ride I did many years ago---an auto from 10 ft agl, with a minimum of 60kts. You only had to demonstrate to a power recovery, although it was somewhat easier to run it on.
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I can remember asking my instructor the same question, and an evil grin crossed his face. I knew what that meant... time to go find out the hard way.
At near Vne and 25' in a 206, he rolls off the throttle. Exactly like What Limits says. Hauled on the cyclic to gain altitude and pulled hard on the collective to keep the Nr green. We shot up like a cork, the G forces were huge!! Within a few seconds we were level at 400' and 70 kts. A simple 180 turn and we were into wind for the landing.
About as much fun as you can have with your pants on.
At near Vne and 25' in a 206, he rolls off the throttle. Exactly like What Limits says. Hauled on the cyclic to gain altitude and pulled hard on the collective to keep the Nr green. We shot up like a cork, the G forces were huge!! Within a few seconds we were level at 400' and 70 kts. A simple 180 turn and we were into wind for the landing.
About as much fun as you can have with your pants on.
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At Shawbury, on the basic course, we used to practice low level "engine offs" in the Gazelle and demo them to students.
Students weren't required to practice, although they did do "full-down" EOLS quite routinely.
Its twenty three years ago for me but I think we did them at 100' agl and 120 kts or more (not NOE but we were interested in the technique without undue risk to the aircraft and occupants).
The student was always briefed to retard the throttle only after a count down of "Identify the throttle..... out of the gate..... 3 - 2 - 1 - NOW!" The idea was to convert speed to height and convert to a variable flare EOL. The aircraft would climb to about 400 feet.
A colleague of mine briefed his student at Ternhill, did a dry run through to check his understanding, took off for a positioning circuit and ran on in, descending and accelerating..........
"Identify the throttle"......says the QHI.
Quick as a flash, the student's hand shot upwards, immediately chopped the throttle and they landed in a farmer's field about half a mile from Ternhill airfield!
Students weren't required to practice, although they did do "full-down" EOLS quite routinely.
Its twenty three years ago for me but I think we did them at 100' agl and 120 kts or more (not NOE but we were interested in the technique without undue risk to the aircraft and occupants).
The student was always briefed to retard the throttle only after a count down of "Identify the throttle..... out of the gate..... 3 - 2 - 1 - NOW!" The idea was to convert speed to height and convert to a variable flare EOL. The aircraft would climb to about 400 feet.
A colleague of mine briefed his student at Ternhill, did a dry run through to check his understanding, took off for a positioning circuit and ran on in, descending and accelerating..........
"Identify the throttle"......says the QHI.
Quick as a flash, the student's hand shot upwards, immediately chopped the throttle and they landed in a farmer's field about half a mile from Ternhill airfield!
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So I guess that the inertia in the rotor gives you a chance to gain some altitude and at least accept a more reasonable landing spot rather than 12 o'clock below the nose.
Not so possible in a low inertia rotor like and R22 or H300 for example.
Not so possible in a low inertia rotor like and R22 or H300 for example.
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Mungo5,
The thing about low inertia rotors is that they are low inertia, which is good and bad!
The low inertia rotor can be speeded up more quickly than a high inertia equivalent by a flare. The flare will transfer kinetic energy from forward air speed into rotor rpm AND the potential energy represented by height. For the same situation but low or high inertia MRs, rotor rpm will be raised more by the same flare situation for the low inertia system.
The problem with low inertia MRs is that they cannot store the same amount of energy (without overspeeding the rotor system). So the final EOL is likely to be more difficult, probably at higher speed and with more of a requirement for a flare during the EOL.
The thing about low inertia rotors is that they are low inertia, which is good and bad!
The low inertia rotor can be speeded up more quickly than a high inertia equivalent by a flare. The flare will transfer kinetic energy from forward air speed into rotor rpm AND the potential energy represented by height. For the same situation but low or high inertia MRs, rotor rpm will be raised more by the same flare situation for the low inertia system.
The problem with low inertia MRs is that they cannot store the same amount of energy (without overspeeding the rotor system). So the final EOL is likely to be more difficult, probably at higher speed and with more of a requirement for a flare during the EOL.
Last edited by Helinut; 26th Nov 2008 at 23:12. Reason: typos
So I guess that the inertia in the rotor gives you a chance to gain some altitude and at least accept a more reasonable landing spot rather than 12 o'clock below the nose.
Not so possible in a low inertia rotor like and R22 or H300 for example.
Not so possible in a low inertia rotor like and R22 or H300 for example.
You gain altitude by converting your forward speed into a climb.
You still wouldn't be able to gain a whole lot of altitude in a R22 because the whole thing is pretty light (haven't tried it), and you probably wouldn't gain very much in a 300 either because it's max speed is about 30 knots or so.
I did try it in a 44 once at the robinson factory. We entered at 110kts or so and easily gained over 400ft.
So I guess that the inertia in the rotor gives you a chance to gain some altitude and at least accept a more reasonable landing spot rather than 12 o'clock below the nose.
Not so possible in a low inertia rotor like and R22 or H300 for example.
Not so possible in a low inertia rotor like and R22 or H300 for example.
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I did try it in a 44 once at the robinson factory. We entered at 110kts or so and easily gained over 400ft.
I was thinking of R22, its rotor system and 'hauling back cyclic' or 'pulling hard' collective. Hmm. Hmm. No thanks.
I did use gentle aft cyclic sometimes for bit of extra climb @50kt, when taking off from end of Charlie pattern patch on hot day (thus safer height over poles/cables). I'm yet to learn to execute all the fiddling with controls and judging the length of flare, height, coordination doing autos to hover. As I'm back to UK, maybe in two years or so next time I'd do more rotary training..
Money, ehm.Didn't expect R44 to be much better/safer at such maneuvre as the mast is about the same and I've read enough here about all the nasty stuff on Robinsons. Plus the inertia thing - less than R22, but still.
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When I was doing ab-initio instructing for CPL students, I used to demonstrate engine offs in the R22 from downwind 20 feet at around 70-90 knots and doing it like that there's no need for any zoom climb; just lower the lever as you initiate a gentle flare and carry out a 180 degree turn with 30 degrees of bank. You end up doing a fairly gentle engine off, usually to a zero speed touchdown abeam the start point. Naturally this was only demonstrated to students nearing the end of their course.
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MK10,
Precisely! The only difference is that you're doing it without the benefit of engine power to hover at the end. Even with the low inertia rotor of the R22 the flare affect helps to delay RRPM decay.
Precisely! The only difference is that you're doing it without the benefit of engine power to hover at the end. Even with the low inertia rotor of the R22 the flare affect helps to delay RRPM decay.
Presumeably with a teethering head if you do pull up with cyclic , maintaining rotor speed with collective ,you need to be careful at the top of climb as you push over so as not to get low g or do you just gradually reduce the airspeed in the climb to 60- 70 kts or so before the inevitable descent.?Have never tried it or seen it demonstrated .Not about to try either without instruction I hasten to add.
R
R
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probably wouldn't gain very much in a 300 either because it's max speed is about 30 knots or so.
Don't mean to be dense.........but
Is that the same process as a down wind quick stop, flare/lower lever/turn??
Is that the same process as a down wind quick stop, flare/lower lever/turn??
Soggy boxer one has explained it.
you need to be careful at the top of climb as you push over so as not to get low g
In advanceed techniques one can extenuate further with techniques from super low level at eight feet or so / high speed to then establish the aircraft in a profile which is mandatory for all EOL's, I. E. the final approach path to a termination area prior to pitch pull (touchdown). Shytorque actually identified that if you read his post carefully.
It really doesn't matter whether you start from fifty, one hundred and fifty, or one thousand and fifty feet, the EOL is made up of three simple steps.
1) Auto-rotational descent, or flight path,
2) Termination area, this is the time for flare and maybe a bit of pitch pull, usually in a lightie it's one foot of altitude for every remaining knot of airspeed).
3) Touchdown, (time for prudent collective use to cushion the remaining vertical descent).
all the best tet
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Several things:
Regarding possibility of mast bumping at the top of the zoom climb - it's going to be pretty difficult to generate a lot of negative G at 60 knots, unless you slam down the collective. But the collective at this time in this maneuver will be on the bottom, so all you're left with is the cyclic. Just like you couldn't generate 2G (1 more than you already have) at 60 knots with only the cyclic, you'd be very hard pressed to get down to a G level that's going to make trouble.
Of course, one hopes that the pilot has been properly trained in the whole art of flying helicopters when doing this sort of thing.
Regarding possibility of mast bumping at the top of the zoom climb - it's going to be pretty difficult to generate a lot of negative G at 60 knots, unless you slam down the collective. But the collective at this time in this maneuver will be on the bottom, so all you're left with is the cyclic. Just like you couldn't generate 2G (1 more than you already have) at 60 knots with only the cyclic, you'd be very hard pressed to get down to a G level that's going to make trouble.
Of course, one hopes that the pilot has been properly trained in the whole art of flying helicopters when doing this sort of thing.
Avoid conjecture - read up on helicopter aerodynamics for yourself. Some of the statements here can be described as "coming from experience which may be large yet narrow".
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So given that the donk has quit - and you're maintaining Nr as close to 100% as possible, how much of an Nr % decay would you expect to see after the climb?
I presume that figure is related to the inertia potential of the MR?
I presume that figure is related to the inertia potential of the MR?
how much of an Nr % decay would you expect to see after the climb?