Slope landings.
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Slope landings.
I am wondering what the preferances and the pros and cons of landing on sloping ground are.
Assuming there is no wind and there are no obstructions, and the angle of the slope will allow the four options below.
Example:
In a left skid low heli, what would the preferance be and why ?
1. Left skid on high side of slope.
2. Left skid on low side of slope.
3.Nose facing up the slope.
4.Tail facing up the slope....
Thanks in advance,
Loachy
Assuming there is no wind and there are no obstructions, and the angle of the slope will allow the four options below.
Example:
In a left skid low heli, what would the preferance be and why ?
1. Left skid on high side of slope.
2. Left skid on low side of slope.
3.Nose facing up the slope.
4.Tail facing up the slope....
Thanks in advance,
Loachy
Gentleman Aviator
Has to be "2"
Best to avoid "up" or "down" on skidded helis - the brakes are never very good!!
Being closer to the hover attitude (ie left skid down for left skid low) means less control deflection used (and therefore more deflection/control power remains available) for landing and take off.
Must also consider (you didn't exclude) pilot position. If you're flying from the "downslope" side then you move through a longer arc which can add to psychological effects....
Best to avoid "up" or "down" on skidded helis - the brakes are never very good!!
Being closer to the hover attitude (ie left skid down for left skid low) means less control deflection used (and therefore more deflection/control power remains available) for landing and take off.
Must also consider (you didn't exclude) pilot position. If you're flying from the "downslope" side then you move through a longer arc which can add to psychological effects....
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The slope landing needs the most lateral stick, which depends on how the design is rigged. An easy way to see which direction is best is to locate the stick in a no-wind hover, relative to the lateral stick range (a clipboard held over it, referenced to the side of the window frame helps). Then shutdown and work the stick to each lateral stop. Usually, the stick is rigged so that there is slightly more right stick than left stick but the real answer is different for each helo. If there is more right stick, this favors the left skid downslope, since both the stick and the "natural slope" of the helo favor that direction.
The side with the most lateral stick travel from hover position to the stops is usually the best side to put upslope.
If you have the maintenance manual, check the lateral stick rnge in degrees. For each degree of lateral stick from the hover point, you can get about 1 to 1.25 degrees of slope. If there are 8 degrees from hover to the right stop, you can get about 8 to 10 degrees of slope in that direction.
The side with the most lateral stick travel from hover position to the stops is usually the best side to put upslope.
If you have the maintenance manual, check the lateral stick rnge in degrees. For each degree of lateral stick from the hover point, you can get about 1 to 1.25 degrees of slope. If there are 8 degrees from hover to the right stop, you can get about 8 to 10 degrees of slope in that direction.
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Notwithstanding the above, and if nothing else prevents it I also offset the tail slightly down the slope - just gives me a warmer feeling about the clearance, although this is not particularly scientific
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Skids are designed for forward stresses, not rearward. Example: running landings are fine, but catch the back of the skid on something as you wheel it backwards into the hangar and the skid crossbar-to-fuselage brackets can suddenly break off. Been there, seen that.
Therefore: don't park facing uphill.
Skids are also designed to allow easy slipping in the forward direction.
Therefore: don't park facing downhill.
Therefore: don't park facing uphill.
Skids are also designed to allow easy slipping in the forward direction.
Therefore: don't park facing downhill.
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Thanks NL for the great explanation,
Some helo models like the 520N are pretty tail heavy. If you land them facing uphill, it might fall on the tail skid once the pilot gets out of the cockpit. Or when he comes back from a nice walk in the forest.
Also, dont forget, if you are going to spend a couple hours waiting there, ask yourself if you will be confortable sitting and waiting in the helicopter.
But first of all, take your time, if you dont feel comfortable with it, take it back up. Try it differently.
Cheers,
YL
Some helo models like the 520N are pretty tail heavy. If you land them facing uphill, it might fall on the tail skid once the pilot gets out of the cockpit. Or when he comes back from a nice walk in the forest.
Also, dont forget, if you are going to spend a couple hours waiting there, ask yourself if you will be confortable sitting and waiting in the helicopter.
But first of all, take your time, if you dont feel comfortable with it, take it back up. Try it differently.
Cheers,
YL
Depends upon which way round the blades go. US helis that turn CClockwise ( when viewed from above) hang left skid low. therefore park it right skid up the slope. The reverse is true for Eurocopters. Most machines will take 10 deg x slope and about 12 deg upslope.
Good tip, on soft ground do not get out of the machine with blades turning. It is embarrasing to walk away and watch the tail hit the ground as the rear of the skids sink in on an upslope landing. When getting out stand on the skids if you are unsure and gingerly step off !!!
Good tip, on soft ground do not get out of the machine with blades turning. It is embarrasing to walk away and watch the tail hit the ground as the rear of the skids sink in on an upslope landing. When getting out stand on the skids if you are unsure and gingerly step off !!!
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The best slope to land on (i.e. easiest for the aircraft and the pilot) is the one that matches the hover attitude.
Normally this means a combination of low skid downhill and slightly nose up - so you land diagonally. This means the least control movement.
Whatever you do, take it very carefully and if you reach the limit of cylic movement, you must lift carefully off the slope and find somewhere else to land because you have just found the aircraft limit. A crosswind, the C of G and sometimes a fat boy or a daddy-long-legs in the other seat will have a bearing on the limit of cyclic, as well as the steepness of the slope. No names mentioned, but I have flown with a few folk who bodily blocked the full movement of cyclic - a steep slope is the time you find this out....
Normally this means a combination of low skid downhill and slightly nose up - so you land diagonally. This means the least control movement.
Whatever you do, take it very carefully and if you reach the limit of cylic movement, you must lift carefully off the slope and find somewhere else to land because you have just found the aircraft limit. A crosswind, the C of G and sometimes a fat boy or a daddy-long-legs in the other seat will have a bearing on the limit of cyclic, as well as the steepness of the slope. No names mentioned, but I have flown with a few folk who bodily blocked the full movement of cyclic - a steep slope is the time you find this out....
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Question for Nick, (or anybody else that knows)
You explained us how we could calculate the number of degrees of the slope we could land on according to the control rigging.
Wouldnt the width of the skids and the height of the CG play a part in the equasion? Or, are every designed aircrafts rigged to make sure we can not land on a slope where a static roll over would be likely to occur?
What are the RFM limits based on?
Thanks
YL
You explained us how we could calculate the number of degrees of the slope we could land on according to the control rigging.
Wouldnt the width of the skids and the height of the CG play a part in the equasion? Or, are every designed aircrafts rigged to make sure we can not land on a slope where a static roll over would be likely to occur?
What are the RFM limits based on?
Thanks
YL
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I think your assumption is correct, static rollover occurs outside the range we are talking about for slope landings. However I'm surprised Nick is focussing exclusively on stick movement, I've always followed the Shy Torque philosophy.
Seems to me the tilt of the heli at hover ought to be an issue. Let's say your skids are 5ft (60in) wide and you hover with one skid 3in low, that looks like a 3deg built in slope you have to overcome in one direction. If you're talking about stick movements of 8-10deg, that's quite a significant factor.
Maybe manufacturers always allow pro rata extra movement in the TR drift avoidance direction to equalise this, but it's still easier to go with the tilt IMHO. Minimises that rather uncomfortable half on half off time.
Seems to me the tilt of the heli at hover ought to be an issue. Let's say your skids are 5ft (60in) wide and you hover with one skid 3in low, that looks like a 3deg built in slope you have to overcome in one direction. If you're talking about stick movements of 8-10deg, that's quite a significant factor.
Maybe manufacturers always allow pro rata extra movement in the TR drift avoidance direction to equalise this, but it's still easier to go with the tilt IMHO. Minimises that rather uncomfortable half on half off time.
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puntosaurus and ylhelico,
The flight manual limits are established by landing on ever increasing slopes until the lateral stick stops are contacted. I have never heard of static rollover margin being lower than stick margin.
The Static rollover angle for most helos is far greater than the slope limit due to stick margins, almost never is the static rollover the limit to slopes. A typical stick margin limit might be 8 to 16 degrees (measured as the maximum slope one can land on without touching the lateral stick stops). A typical static rollover angle might be 30 degrees. One can calculate the static rollover angle by simply drawing a cross section of the helicopter, with a line through the cg extending thru the skid or wheel. Here are two examples:
Remember, the actual slope capability on any given day can be less than the flight manual limit, because the wind and lateral CG as well as the slope material (friction coefficient) all affect the true capability.
The flight manual limits are established by landing on ever increasing slopes until the lateral stick stops are contacted. I have never heard of static rollover margin being lower than stick margin.
The Static rollover angle for most helos is far greater than the slope limit due to stick margins, almost never is the static rollover the limit to slopes. A typical stick margin limit might be 8 to 16 degrees (measured as the maximum slope one can land on without touching the lateral stick stops). A typical static rollover angle might be 30 degrees. One can calculate the static rollover angle by simply drawing a cross section of the helicopter, with a line through the cg extending thru the skid or wheel. Here are two examples:
Remember, the actual slope capability on any given day can be less than the flight manual limit, because the wind and lateral CG as well as the slope material (friction coefficient) all affect the true capability.
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Thanks for those diagrams Nick, they are very useful - I wish I had similar when I was instructing on the military Puma!
The SA330J Puma is notorious for its propensity to "lift her inside leg" on the ground due to it's high C of G and narrow track u/c. That aircraft has a shim pack underneath the cyclic to prevent excessive lateral movement by the the pilot. Even so, I know of one case where quite an experienced RAF pilot (ex Wessex, IIRC) rolled the aircraft onto its side whilst enthusiastically turning the aircraft onto the runway for what should have been his first solo takeoff....
I still sometimes get laughed at by non-Puma pilots because a dozen years or so after I last flew that type, I still cannot help myself applying in-turn cyclic during ground taxying "for the wife and kids" - even on fixed wing at walking speed! Self preservation rules OK
The SA330J Puma is notorious for its propensity to "lift her inside leg" on the ground due to it's high C of G and narrow track u/c. That aircraft has a shim pack underneath the cyclic to prevent excessive lateral movement by the the pilot. Even so, I know of one case where quite an experienced RAF pilot (ex Wessex, IIRC) rolled the aircraft onto its side whilst enthusiastically turning the aircraft onto the runway for what should have been his first solo takeoff....
I still sometimes get laughed at by non-Puma pilots because a dozen years or so after I last flew that type, I still cannot help myself applying in-turn cyclic during ground taxying "for the wife and kids" - even on fixed wing at walking speed! Self preservation rules OK
Shy Torque:
Why would you get laughed at?
Back when Pan Am was running a schedule helicopter service between Manhattan to JFK, the ships would land out on a taxiway and then have to ground-taxi to Pan Am's Worldport. I used to see those little 222's hauling ass inbound, coming around the corner with the inside wheel completely off the ground. I used to watch them from my airplane sometimes and think to myself, "Doesn't that lean to the outside of the turn bother them? Can't they feel that?" As a motorcyclist, I wouldn't be able to stand it. And I used to wonder when they were going to roll one over. Never did though AFAIK.
Into-the-turn cyclic sounds like a pretty good idea to me, Shy.
I still sometimes get laughed at by non-Puma pilots because a dozen years or so after I last flew that type, I still cannot help myself applying in-turn cyclic during ground taxying "for the wife and kids"
Back when Pan Am was running a schedule helicopter service between Manhattan to JFK, the ships would land out on a taxiway and then have to ground-taxi to Pan Am's Worldport. I used to see those little 222's hauling ass inbound, coming around the corner with the inside wheel completely off the ground. I used to watch them from my airplane sometimes and think to myself, "Doesn't that lean to the outside of the turn bother them? Can't they feel that?" As a motorcyclist, I wouldn't be able to stand it. And I used to wonder when they were going to roll one over. Never did though AFAIK.
Into-the-turn cyclic sounds like a pretty good idea to me, Shy.
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The most expeditious way of landing on a slope is to land (in you case) slightly upslope and slightly left skid low at a 45 degree angle, a small (1-2Kt) run on makes life easier. There is a lot of advice out there about these things but this should be akin to falling off a log... If you are flying a rigid rotor then limit your inslope cyclic to the minimum required.
Teeteringhead is correct in what he says reference psychological effects but I assume you fly from the RHS - Practise, Practise, Practise...
Teeteringhead is correct in what he says reference psychological effects but I assume you fly from the RHS - Practise, Practise, Practise...
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Always wondered:
Flying a machine with oleo equipped gear (S76), could you transfer enough of the aircraft weight to the downhill oleo unloading the upslope one. This upslope oleo could then extend causing you to exceed the lateral cyclic limits.
Maybe this one's for you Nick.
Flying a machine with oleo equipped gear (S76), could you transfer enough of the aircraft weight to the downhill oleo unloading the upslope one. This upslope oleo could then extend causing you to exceed the lateral cyclic limits.
Maybe this one's for you Nick.
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Having spent a few years using the S-76 for SAR and mountain flying training, I can say that in common with most other wheeled helicopters you can do anything wrong if you try hard enough.
However, a good, sensible pilot will take the landing slowly and keep flying the heli all the time, monitoring the AI to check the RFM slope limits aren't exceeded, so this shouldn't be a problem.
I can only see this happening in practice if the downhill oleo "stuck" extended, then suddenly gave, as the collective was lowered further. BTW, it helps settle the oleos if the pilot gently makes the aircraft "jiggle" a little.
However, a good, sensible pilot will take the landing slowly and keep flying the heli all the time, monitoring the AI to check the RFM slope limits aren't exceeded, so this shouldn't be a problem.
I can only see this happening in practice if the downhill oleo "stuck" extended, then suddenly gave, as the collective was lowered further. BTW, it helps settle the oleos if the pilot gently makes the aircraft "jiggle" a little.