Leaning for high density altitude takeoffs and climbs
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Leaning for high density altitude takeoffs and climbs
I'm going to be heading over to the States again for some hour building, this time visiting the South West - Grand Canyon, Sedona and a few other high altitude airports.
Having read some basic guides on mountain flying all of them seem to recommend leaning the engine for takeoff and climb. I was always taught that leaning the engine at 100% takeoff power is plain dangerous.
Any thoughts? Also would be interested to hear from other folks who have done hour building by flying from Florida up to the South West/CA and back again.
Thanks
Having read some basic guides on mountain flying all of them seem to recommend leaning the engine for takeoff and climb. I was always taught that leaning the engine at 100% takeoff power is plain dangerous.
Any thoughts? Also would be interested to hear from other folks who have done hour building by flying from Florida up to the South West/CA and back again.
Thanks
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Boy oh boy.
I think that you need some serious time with a instructor before you go near them thar hills, or you are likely to kill yourself.
If you don't lean at high density altitudes, you will not develop full power.
There are many, many, other factors in mountain flying that mandate an appropriate amopunt of time with a qualified and experienced instructor.
I think that you need some serious time with a instructor before you go near them thar hills, or you are likely to kill yourself.
If you don't lean at high density altitudes, you will not develop full power.
There are many, many, other factors in mountain flying that mandate an appropriate amopunt of time with a qualified and experienced instructor.
True enough on both counts.
None of the rental places in the US will hire you an aeroplane to fly to places like that without a high altitude checkout. Yes you do need to lean for best power (and to stop the plugs fouling), the local instructors understand that those of us who fly in the UK won't have been taught how, and will make sure that you understand it before they let you out on your own.
It actually very interesting - and a new skill as you gently tweak mixture for best power during a slow and ponderous take-off run from somewhere like Grand Canyon.
The other thing is don't forget that power in any case will be far down on what you're used to. So, hire something like a C152 only if planning to fly solo, and something like a Warrior for 2 people.
G
None of the rental places in the US will hire you an aeroplane to fly to places like that without a high altitude checkout. Yes you do need to lean for best power (and to stop the plugs fouling), the local instructors understand that those of us who fly in the UK won't have been taught how, and will make sure that you understand it before they let you out on your own.
It actually very interesting - and a new skill as you gently tweak mixture for best power during a slow and ponderous take-off run from somewhere like Grand Canyon.
The other thing is don't forget that power in any case will be far down on what you're used to. So, hire something like a C152 only if planning to fly solo, and something like a Warrior for 2 people.
G
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I tend to echo F3G's comments.
You should really have a chat with an instructor (and preferrably one who has actually experienced the conditions)
Leaning is most important when dealing with these higher altitude airfields. Leaning tothe peak power available is paramount in the conditions you're likely to encounter.
Last year I flew from USA East coast across to California and back (Grumman AA5B - beautiful machine) - Several airfields visited would have proved very difficult if not impossible from which to depart and climb without proper leaning - eg Rawlings Municiple (KRWL - Wyoming) - 7008ft (2156m) of runway. Altitude - 6813ft ASL. Airtemp 115degF - Nil wind. Reported density altitdue 10,000ft!
You'll certainly need to properly understand Density Altitude and the consequences of "Hot & High".
Don't be put off - It's a great country to fly in - This year it's Connecticut (Bridgeport to Texas and back - Yahooo!
)
You should really have a chat with an instructor (and preferrably one who has actually experienced the conditions)
Leaning is most important when dealing with these higher altitude airfields. Leaning tothe peak power available is paramount in the conditions you're likely to encounter.
Last year I flew from USA East coast across to California and back (Grumman AA5B - beautiful machine) - Several airfields visited would have proved very difficult if not impossible from which to depart and climb without proper leaning - eg Rawlings Municiple (KRWL - Wyoming) - 7008ft (2156m) of runway. Altitude - 6813ft ASL. Airtemp 115degF - Nil wind. Reported density altitdue 10,000ft!
You'll certainly need to properly understand Density Altitude and the consequences of "Hot & High".
Don't be put off - It's a great country to fly in - This year it's Connecticut (Bridgeport to Texas and back - Yahooo!
)
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As an example, the underlying idea is that Lycoming authorise leaning to peak EGT at power settings below 75% of max rated HP, for certain engines.
So, if the density altitude at departure is such that the engine will not make more than 75% rated power anyway (one needs to refer to the engine performance charts for this, but (on a NON turbocharged engine obviously) it's of the order of a few thousand feet airfield elevation) then one leans - on the runway - for max revs (if fixed pitch prop) or for peak EGT (if VP prop).
So, one needs to understand the engine performance charts, which aren't necessarily provided in the handbook.
And how to calculate the density altitude, given airfield elevation, baro pressure, and temperature. This is done using a slide rule or some other calculator, or using a takeoff performance chart which has curves on it for all these factors.
So, if the density altitude at departure is such that the engine will not make more than 75% rated power anyway (one needs to refer to the engine performance charts for this, but (on a NON turbocharged engine obviously) it's of the order of a few thousand feet airfield elevation) then one leans - on the runway - for max revs (if fixed pitch prop) or for peak EGT (if VP prop).
So, one needs to understand the engine performance charts, which aren't necessarily provided in the handbook.
And how to calculate the density altitude, given airfield elevation, baro pressure, and temperature. This is done using a slide rule or some other calculator, or using a takeoff performance chart which has curves on it for all these factors.
Originally Posted by Farmer 1
I believe there are restrictions on flying in the Grand Canyon area, so suggest you check that out before you set your hopes too high.
But without restriction, you can fly into Grand Canyon airport (which is just South of the Canyon) and pick up a tour.
G
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I've flown in that area quite a few times, and every time I was required to demonstrate an approach, landing, and departure at high altitude (which tended to be Big Bear City). Don't even think of doing it without a thorough briefing and training.
You set full power, then lean for max RPM, before takeoff.
An Arrow III is just about OK with two up and some bags. Even then, your rate of climb might not be much (as we expected, and found).
Learn to do density altitude calcuations: the field might be at 6000 feet, but the DA might be a lot higher.
The Grand Canyon is well worth a visit, but you need the special chart for it - the restrictions are complex, and need studying.
We're off there again in April, ho ho.
You set full power, then lean for max RPM, before takeoff.
An Arrow III is just about OK with two up and some bags. Even then, your rate of climb might not be much (as we expected, and found).
Learn to do density altitude calcuations: the field might be at 6000 feet, but the DA might be a lot higher.
The Grand Canyon is well worth a visit, but you need the special chart for it - the restrictions are complex, and need studying.
We're off there again in April, ho ho.
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Also bear in mind that in some hot/high circumstances you may NOT be able to get the a/c airborne ! Always, always, refer to the charts (density alt, performance, runway length, weight) and REALLY calculate your t/o roll and climb perfomance. Rule of thumb 'ah, she'll be right' is a - potentially deadly - no-no. Also, always use ALL runway avail. And definitely get some time with an instructor over there first. You'll be surprised how a 172 can suddenly feel like a heavy 747 laden to the gunwales 
!
PS: I'd also rather rent a 172 (or better still 182) rather than a PA28 for your adventure. The Cessnas have a higher service ceiling - and a bettter view ;-)
!PS: I'd also rather rent a 172 (or better still 182) rather than a PA28 for your adventure. The Cessnas have a higher service ceiling - and a bettter view ;-)
Last edited by 172driver; 22nd Jan 2006 at 17:36.
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Any thoughts?
Also would be interested to hear from other folks who have done hour building by flying from Florida up to the South West/CA and back again.
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3000 ft DA is not at all unusual around California, Nevada etc and in the Rockies. Pete and I landed at places with DA around 10,000 feet. That does test your skills - landing indicates the right speed, but is (and feels) a lot faster. Takeoff is a challenge. Do the sums!
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Wyoming
I learnt to fly in Cheyenne, Wyoming where it is 6,700 feet above sea level. It is essential to lean the engine during the power checks otherwise you won't get off the ground. I flew a 160hp 172 and on some days it was struggle to get airborne, half filled tanks and a stiff headwind helped. The winds at these altitudes can also be a problem, I once heard a guy on the radio saying that he was finding it difficult to keep a positive ground speed. Bad weather can develop VERY quickly around the Rockies.
I survived it and thoroughly enjoyed it but I was flying with some very experienced local flyers.
I survived it and thoroughly enjoyed it but I was flying with some very experienced local flyers.
Best Power Mixture on Landing is NOT Full Rich at altitude
Watch out on those touch and gos.
Mixture Full Rich is drilled in as a before landing check, but does not work that well in a Grumman Cheetah on a Summer day on a 3000' runway at 3937' ASL.
Was able to see the gophers diving into their holes while building airspeed in ground effect
Mixture Full Rich is drilled in as a before landing check, but does not work that well in a Grumman Cheetah on a Summer day on a 3000' runway at 3937' ASL.
Was able to see the gophers diving into their holes while building airspeed in ground effect
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Originally Posted by RatherBeFlying
Watch out on those touch and gos.
Mixture Full Rich is drilled in as a before landing check, but does not work that well in a Grumman Cheetah on a Summer day on a 3000' runway at 3937' ASL.
Was able to see the gophers diving into their holes while building airspeed in ground effect
Mixture Full Rich is drilled in as a before landing check, but does not work that well in a Grumman Cheetah on a Summer day on a 3000' runway at 3937' ASL.
Was able to see the gophers diving into their holes while building airspeed in ground effect
(the municipal golf course is at the end of runway 31).
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We have had two density altitude accidents at two local airfields in Switzerland in the last two years. One is at 3300ft amsl and the other at 2130ft, but the temp in the summer gets up into the 30s. The strip at 2100 ft amsl is Gruyere, with an 800m + grass strip. A 172 went into the trees at the end four-up after refueling. The other one is Saanen and has a 3000ft tarmac strip. A 152 took off to the East, one-up, and didn't make it over the pass. All on-board were killed in both cases.
DA is a most deceptive killer. You can easily get into a mindset of 'this aircraft should be able to get out of here easily', but 20 degrees in temp will make all the difference. Very sobering.
QDM
DA is a most deceptive killer. You can easily get into a mindset of 'this aircraft should be able to get out of here easily', but 20 degrees in temp will make all the difference. Very sobering.
QDM
Originally Posted by IO540
All because the PPL does't include training for proper takeoff performance calculation (IME).
But why on earth should a UK trained pilot have been taught the skills of leaning for best power take-off at 3000+ft density altitude? It's a particular skill for particular parts of the world which, like for example mountain flying, should be learned when needed. The main thing is to make sure that PPLs know there's a difference.
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All because the PPL does't include training for proper takeoff performance calculation (IME).
But why on earth should a UK trained pilot have been taught the skills of leaning for best power take-off at 3000+ft density altitude?
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I suppose in theory a freshly minted PPL could safely fly around the mountains. In practice it's not that simple. For instance, Keef makes a good point, if feels a lot faster when on final. It would be impossible to reproduce that on your average flatland PPL course. Could the UK instructor describe that? Probably not. The first time your new PPL flying the numbers (yeh, right 
) saw his approach he could easily get into a lot of trouble. Climbing out, the sight picture is totally different too, very easy to stall close to the ground and that's not desirable. So in the real world I wouldn't expect a PPL to know how to fly safely in the mountains, which is why I tell them to get some dual with somebody who knows the score. And that isn't a lowland instructor in the US or the UK.
) saw his approach he could easily get into a lot of trouble. Climbing out, the sight picture is totally different too, very easy to stall close to the ground and that's not desirable. So in the real world I wouldn't expect a PPL to know how to fly safely in the mountains, which is why I tell them to get some dual with somebody who knows the score. And that isn't a lowland instructor in the US or the UK.
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''I suppose in theory a freshly minted PPL could safely fly around the mountains.''
Hey Slim - I know you've done a bit of flying in the mountains - no-one has mentioned turbulence yet (30 knots over the tops etc....)
I also support Ghengis' view; PPLs can't be taught everything - for instance I don't believe that US PPLs are taught to land using the crab technique.
Hey Slim - I know you've done a bit of flying in the mountains - no-one has mentioned turbulence yet
(30 knots over the tops etc....)I also support Ghengis' view; PPLs can't be taught everything - for instance I don't believe that US PPLs are taught to land using the crab technique.