Elevation/Density Altitude for Private Pilots
Thread Starter
Elevation/Density Altitude for Private Pilots
Flying around the UK as I do there are not many places that you encounter ground above 3,000ft and our weather is usually pretty cool so generally power issues are not too much of a problem even in an R44 Raven 1.
The recent posts that discussed the R44 that crashed due to an attempt to hover OGE outside of the aircraft limits and the other video clip that was posted about the R44 that crash landed on the mountainside in the US for the same reason got me thinking...
What density altitudes do our fellow Rotorheads, particularly those flying for fun, find themselves operating in around the world where the weather is warm and the ground higher?
Does the ability to hover OGE at 10,000ft on a 30C day make any difference to typical private pilots around the world or not? Should Robinson upgrade the R44 to be able to do this?
CRAN
The recent posts that discussed the R44 that crashed due to an attempt to hover OGE outside of the aircraft limits and the other video clip that was posted about the R44 that crash landed on the mountainside in the US for the same reason got me thinking...
What density altitudes do our fellow Rotorheads, particularly those flying for fun, find themselves operating in around the world where the weather is warm and the ground higher?
Does the ability to hover OGE at 10,000ft on a 30C day make any difference to typical private pilots around the world or not? Should Robinson upgrade the R44 to be able to do this?
CRAN
I didn't notice any issues with power in South Africa (Rand Airport, >5000ft asl) in the R44 except to just keep an eye out for it during take off and landing, but the R22 has its work cut out for it and this was in spring when it was relatively cool.
You couldn't just climb vertically in the 44, (especially with more than 2 pax) you'd want to use your best performance profile.
Had issues with one of the R22s overheating a lot during IGE hover, but that was mechanical. You do have to keep a close eye on MAP during hover exercises though, there's very little extra power to pull if both pilots are near 90kg each.
You couldn't just climb vertically in the 44, (especially with more than 2 pax) you'd want to use your best performance profile.
Had issues with one of the R22s overheating a lot during IGE hover, but that was mechanical. You do have to keep a close eye on MAP during hover exercises though, there's very little extra power to pull if both pilots are near 90kg each.
10000 feet and 30 Celsius.....
I don't think there is anywhere in the world with that kind of temperature and elevation.
I'm based approx 5 degrees north of the equator and when I fly to the big mountain which is about 13000 feet the temperature is usually about 15 Celsius which is still pretty warm considering the high altitude.
I don't think there is anywhere in the world with that kind of temperature and elevation.
I'm based approx 5 degrees north of the equator and when I fly to the big mountain which is about 13000 feet the temperature is usually about 15 Celsius which is still pretty warm considering the high altitude.
10000 feet and 30 Celsius.....
I don't think there is anywhere in the world with that kind of temperature and elevation.
I don't think there is anywhere in the world with that kind of temperature and elevation.
Upper helipad at Armanath 12000ft/+22°C.
Get the approach wrong and lose ETL before in ground effect and you're doomed.Was quite interesting.
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Does the ability to hover OGE at 10,000ft on a 30C day make any difference to typical private pilots around the world or not? Should Robinson upgrade the R44 to be able to do this?
CRAN
CRAN
Doomed-Goodgrief-Doomed 
Muktinath H - 13,180' @ 31° on Sunny summers day 
Ecamp2 H - 22,000' @ -7°; get that DA intooya, serious for any commercial & private Pilots alike 
HappyHappy
Muktinath H - 13,180' @ 31° on Sunny summers day Ecamp2 H - 22,000' @ -7°; get that DA intooya, serious for any commercial & private Pilots alike HappyHappy
In these parts summer is 31 to 39C 5300ft and above, so it certainly makes a difference for planning. Accident statistics show that the overwhelming description by a pilot (commercial and private alike) of what went wrong was loss of power.
Robbie's are the machine of choice and account for two thirds of crashes, logical since they would be the most power constrained.
Expecting a manufacturer to solve a pilot planning problem is putting the cart before the horse. If you can't do maths or read a chart, you may as well just get yourself a machine which has a bit more puff under the cowling so it will have a greater chance of saving your backside.
Robbie's are the machine of choice and account for two thirds of crashes, logical since they would be the most power constrained.
Expecting a manufacturer to solve a pilot planning problem is putting the cart before the horse. If you can't do maths or read a chart, you may as well just get yourself a machine which has a bit more puff under the cowling so it will have a greater chance of saving your backside.
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The Zp is important for all helicopter, but for short powered helicopters as R22 is essential....Many young pilot ( or not) forget the difference between hovering IGE and OGE. The difference is a rotor diameter altitude and 7 percent of power...
If due to the load and Zp, you are full power for the hovering and take off , you can't hovering OGE. that's all !
After a while, when you have burned some fuel, you earn some percent...BUT you need to burn minimum 7 per cent of your load to perform a hoveing OGE.
Then, depend of the OAT and pressure....Little be more, little be less
If not, and you try to hovering Out Ground effect, The FAA name this mistake "SWP" Settling with power...
If due to the load and Zp, you are full power for the hovering and take off , you can't hovering OGE. that's all !
After a while, when you have burned some fuel, you earn some percent...BUT you need to burn minimum 7 per cent of your load to perform a hoveing OGE.
Then, depend of the OAT and pressure....Little be more, little be less
If not, and you try to hovering Out Ground effect, The FAA name this mistake "SWP" Settling with power...
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The performance charts in the aircraft flight manual should be all that one needs to calculate the weight restrictions/limits when working hot and high.
When departing from a lower altitude take off point to a higher altitude landing point, using the standard lapse rate for approximate temps at the landing site can be used to determine the max landing weight up there.
Working out expected fuel burn for the trip, one can determine with some degree of accuracy the max departure weight for the mission.
Combine that with the standard mountain/high altitude operating procedures and you have a workable plan. Well, Plan "A" anyway. Always have a Plan "B" and Plan "C" and so on for unexpected encounters along the way.
When departing from a lower altitude take off point to a higher altitude landing point, using the standard lapse rate for approximate temps at the landing site can be used to determine the max landing weight up there.
Working out expected fuel burn for the trip, one can determine with some degree of accuracy the max departure weight for the mission.
Combine that with the standard mountain/high altitude operating procedures and you have a workable plan. Well, Plan "A" anyway. Always have a Plan "B" and Plan "C" and so on for unexpected encounters along the way.
Thread Starter
I guess what I'm really asking of the piston drivers out there:
(a) Are you happy with naturally aspirated piston engines that struggle after around 5,000ft pressure altitude on a standard day?
(b) Would you prefer a turbo normalised engine which would make sea level power up to above 15,000ft pressure altitude?
Thanks for the replies,
CRAN
(a) Are you happy with naturally aspirated piston engines that struggle after around 5,000ft pressure altitude on a standard day?
(b) Would you prefer a turbo normalised engine which would make sea level power up to above 15,000ft pressure altitude?
Thanks for the replies,
CRAN
Cran....what about strapping on a couple of Rockets
All Helicopters run out of puff - ALL of em; at X - AUW at some altitude & temp.
If You think the Crapinson 22 runs out of puff fast, try flying an H269 or a Franklin engined 47D 
It is not about pumping in more steroids, NO
It is only about knowing thy machine & thyself & NEVER, EVER exceeding either limitations 
Fly her within the RFM flight envelope & You'll be OK, it really is that simple
Happy landings
All Helicopters run out of puff - ALL of em; at X - AUW at some altitude & temp.
If You think the Crapinson 22 runs out of puff fast, try flying an H269 or a Franklin engined 47D It is not about pumping in more steroids, NO
It is only about knowing thy machine & thyself & NEVER, EVER exceeding either limitations Fly her within the RFM flight envelope & You'll be OK, it really is that simple Happy landings
NEVER, EVER exceeding either limitations
I have no doubt that many pilots become complacent, but having some wiggle room would be nice in many cases.
Cran, it would probably do well to have more power, but does a turbo have that much more power output on existing engines to justify the extra weight and cost?
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When i do my "mountain training" on Turbine helicopter ALouette II ( not a robbie...), in the process i have to check the abacus temp/Zp for the GO/NOGO landing decision.
After the check, i say : NOGO, my instructor say : OK Good decision, but we have to try to GO.....
And we GO
But we know we are at the limits...
After the check, i say : NOGO, my instructor say : OK Good decision, but we have to try to GO.....
And we GO
But we know we are at the limits...
Thread Starter
WillyPete/VF,
Thanks for the responses.
VF; you are of course correct. Anyone that fails to understand the performance limitations of a helicopter will find that their performance problems are very short lived! Private pilots and commercial guys alike must understand and stick to these limits, you'll get no qualms from me on that matter. However, the point I am trying to get to with this thread isn't the skill and discipline of experienced expert commercial pilots that deal daily with extreme operations of the edge of the performance curves, but rather to understand whether design traits of an aircraft can be improved to help the infrequently flying private pilot population avoid trouble given their limitations.
I think we would all agree that power gets you out of trouble in most situations in a helicopter. The problem piston pilots face is that the performance of the machines is marginal even for relatively benign operations.
If you take the Robinson R44 Raven 1 for example, the O-540-F1B5 (205hp/225hp) carburetted version. This machine can only execute a nil wind OGE hover at max gross weight on a 20C day up to 500ft! Therefore, when flying with four normal size adult passengers and 2 hours of fuel you have very limited performance. If you factor in limited pilot experience and currency surely this is a recipe for trouble?
The R44 Raven 2, uses an angled valve engine that breathes more freely and extends this performance to a 2,600ft OGE hover ceiling at MGW on a 20C day, but surely even in cool low green lands of the UK this is pretty limited performance.
How many mishaps would have been avoided if the machine could climb vertically at 10,000ft on a 20C day and hover OGE at this level?
WillyPete:
I agree that the cost, complexity and weight of turbo-normalised piston engines is somewhat of a downside. However, if this is properly taken into account during the design phase, I wonder if the overall effect would be a positive one?
For existing aircraft piston engines, turbocharging is generally used to maintain performance at altitude rather than increase power. The naturally aspirated versions of the IO-540 can make 300hp+, with the turbo'd versions offering 350hp, but weighing about 100lb more and being less fuel efficient on account of the low compression pistons. However, naturally aspirated engines performance lapse the moment you get off the ground, to around 60% at 10,000ft whereas a turbo engine will maintain its full performance to 20,000ft.
The major benefit of the 'Robinson de-rate' of the engines, is that they generally maintain a degree of performance up to a few thousand feet, older designs (and some newer ones) that have squeezed more out of the engines really struggle once away from the ground or on warmer days.
The Cabri G2 can't hover at all out of ground effect on a 20C day at MGW!
When you consider the performance penalties that naturally aspirated engines suffer at modest DA conditions, then all of a sudden the sea-level weight penalty doesn't seem so bad to me.
Happy to learn what others think?
Thanks for the responses.
VF; you are of course correct. Anyone that fails to understand the performance limitations of a helicopter will find that their performance problems are very short lived! Private pilots and commercial guys alike must understand and stick to these limits, you'll get no qualms from me on that matter. However, the point I am trying to get to with this thread isn't the skill and discipline of experienced expert commercial pilots that deal daily with extreme operations of the edge of the performance curves, but rather to understand whether design traits of an aircraft can be improved to help the infrequently flying private pilot population avoid trouble given their limitations.
I think we would all agree that power gets you out of trouble in most situations in a helicopter. The problem piston pilots face is that the performance of the machines is marginal even for relatively benign operations.
If you take the Robinson R44 Raven 1 for example, the O-540-F1B5 (205hp/225hp) carburetted version. This machine can only execute a nil wind OGE hover at max gross weight on a 20C day up to 500ft! Therefore, when flying with four normal size adult passengers and 2 hours of fuel you have very limited performance. If you factor in limited pilot experience and currency surely this is a recipe for trouble?
The R44 Raven 2, uses an angled valve engine that breathes more freely and extends this performance to a 2,600ft OGE hover ceiling at MGW on a 20C day, but surely even in cool low green lands of the UK this is pretty limited performance.
How many mishaps would have been avoided if the machine could climb vertically at 10,000ft on a 20C day and hover OGE at this level?
WillyPete:
I agree that the cost, complexity and weight of turbo-normalised piston engines is somewhat of a downside. However, if this is properly taken into account during the design phase, I wonder if the overall effect would be a positive one?
For existing aircraft piston engines, turbocharging is generally used to maintain performance at altitude rather than increase power. The naturally aspirated versions of the IO-540 can make 300hp+, with the turbo'd versions offering 350hp, but weighing about 100lb more and being less fuel efficient on account of the low compression pistons. However, naturally aspirated engines performance lapse the moment you get off the ground, to around 60% at 10,000ft whereas a turbo engine will maintain its full performance to 20,000ft.
The major benefit of the 'Robinson de-rate' of the engines, is that they generally maintain a degree of performance up to a few thousand feet, older designs (and some newer ones) that have squeezed more out of the engines really struggle once away from the ground or on warmer days.
The Cabri G2 can't hover at all out of ground effect on a 20C day at MGW!
When you consider the performance penalties that naturally aspirated engines suffer at modest DA conditions, then all of a sudden the sea-level weight penalty doesn't seem so bad to me.
Happy to learn what others think?
Last edited by CRAN; 23rd Jan 2017 at 12:08.
Namaste CRAN.........in the AS305B3e (H125) @ ISA +25º above 22,000' You don't have HOGE, barely HIGE with 2 x POB + 50kgs GoJuice + 25kgs stuff, available power is 40% torque if Your lucky....yikes your damn limited! Plus Your up against the Power pedal bump stop so a double whammy
So with power; just like a 269, 22 or G2 at sealevel same damn problem So the power margin limitation problems are exactly the same manage what You have wisely
Happy landings
so a double whammySo with power; just like a 269, 22 or G2 at sealevel same damn problem
So the power margin limitation problems are exactly the same manage what You have wisely Happy landings
CRAN..............exactly, glad You see (finally) 
the power margin of a 44 @ 1,500' is the same as a 125 @ 10,000'
the more steroids (power) you got, (turbo, rocket boosters) the more Your gonna load her up & still You'll run out of puff
Your most welcome Brother
the power margin of a 44 @ 1,500' is the same as a 125 @ 10,000' the more steroids (power) you got, (turbo, rocket boosters) the more Your gonna load her up & still You'll run out of puff
Your most welcome Brother