• If You Are Having Trouble Logging In with Your Old Username and Password, Please use this Forgot Your Password link to get re-established.
  • Hey! Be sure to login or register!

Headed West, When to Lean?

Anne

Registered User
SE Michigan
I'm headed west along I-80 from Ann Arbor to Minden NV in June. I'm thinking that at some point I'll be over terrain that will be high enough I'll have to lean my engine to maintain power. How will I know when to do that? Do I also keep it lean for landing and takeoff? Any other advice?

Thanks!

Anne.
 
Anne,

You should be leaning in the east too!

sj

What SJ said.

According to the PA-18 150hp For 1974 and Later POH

page 17 (TAKEOFF, CLIMB AND STALLS): "...mixture full rich, except a minimum amount of leaning is permitted for smooth engine operation when taking off at high elevation."

page 18 (CRUISING): "...The mixture should be leaned when 75% power or less is being used. If any doubt exists as to the amount of power being used, the mixture should be in the FULL RICH position for all operations."

page 19 (APPROACH AND LANDING): "...The mixture should be full rich,..."

From a real world prospective anytime I'm taking off from an altitude of 4,000 feet or higher I lean for best power and then go a small amount richer. On the approach to landing I'll gradually richen the mixture to whatever setting I'd normally use for takeoff at the altitude for that airport. YMMV.
 
Anne,

You should be leaning in the east too!

sj

I do lean at cruise, but not for takeoff or landing. I had one mountain flying lesson many years ago in Phoenix where the DA was pretty high. Even though airport elevation was 1000' MSL, it was hot, and the instructor leaned the engine for takeoff, then we left it there the rest of the lesson. Is that normal procedure in the mountains? Looking at my route westbound, I'll be getting into higher elevation than I'm used to here at 839' MSL.

Anne.
 
I do lean at cruise, but not for takeoff or landing. I had one mountain flying lesson many years ago in Phoenix where the DA was pretty high. Even though airport elevation was 1000' MSL, it was hot, and the instructor leaned the engine for takeoff, then we left it there the rest of the lesson. Is that normal procedure in the mountains? Looking at my route westbound, I'll be getting into higher elevation than I'm used to here at 839' MSL.

Anne.

Density Altitude is what I use for determining if I lean for takeoff, I just didn't want to overly complicate the discussion. I have a DA display in both the SQ2 (in the Dynon Skyview) and the 185 (in the CO Guardian) so there is no math involved on my part.

Leaning for cruise in the mountains is no different then leaning for cruise in the flatlands, or anywhere else. You probably have some AGL that you use at home before you lean in cruise, along with a power setting. It works the same way in the mountains. So for instance, if you are taking off at a 4,000ft MSL DA airport, and you lean for takeoff, and your flight only takes you to 5,000 MSL (1,000 ft AGL) you wouldn't lean for cruise any differently here then you would when flying 1,000 ft AGL at home. If you are climbing to 12,000ft MSL, well you will be doing some more leaning, just as you would at home if you went to 12,000ft MSL.

At some altitude (and above) your engine will only be able to produce 75%-Lycoming, 65%-Continental at full throttle so leaning to best power under any/all situations is acceptable (assuming no restriction in your POH of course).
 
It can be a scary thought thinking about high altitude airports on hot days; how to keep from damaging the engine?

A lesson I learned in lower performing aircraft was that you need to start by choosing the first few airports for having some runway length!!!

I don't think we need to discuss knowing your aircraft, as you have that down. I will bet you can almost lean by the position of the mixture control for home... that will help!

You do not need to be precise for takeoff, I like to be close on the RICH side. If landing for fuel, and departing right away, I simply push the mixture in a little from cruise, (think 10-20%), and leave it there for landing. When I shut down I eyeball where that mixture is. That is my start position.

On run up I get a feel for the engine, is she doggy or is she sharp and hot? (do you have egt and/or cht?). If she is doggy, I lean a smidgen. If sharp I might push till doggy and split the difference. That becomes my takeoff setting.

One thing folks will do is on run up is to go high power and lean on the ground before takeoff, I hate doing that, hard on the prop.

Each aircraft is different, so the mixture position for each elevation/temperature will be different. More rich than cruise for takeoff, but not full if you are high and hot, but it is trial and error.

Do NOT go full rich for landing when at 6,000 feet...

also, once airborne the first couple of times, leave full power and lean to about 100-150 degrees rich of peak and use that as a guide. If you have room, move to full rich in cruise (or go full power at altitude) and then lean back... where is she running smooth?

If you do have egt, watch the temperature for home operations and try to lean for that. It is trial and error, practice and caution towards keeping her cool while getting power enough to depart.

You will have to lean on the ground often when high/hot also

In the immortal words of SB: YMMV!
 
If you don't lean on take off at elevation you will one day find yourself crappin' your pants an wondering if you're gonna climb out over obstacles - then you realize your error, you lean, and its a whole new airplane. Conversely, if you forget to richen the mixture on descent and arrival, especially at elevation, you may pull power and find you get a surprise deadstick landing. There are those that have and those that will. Ask me how I know this... :)
 
I am one of the seemingly few Rotax 912 pilots with a manual mixture control, and for the last few months I have been stumbling my way through figuring out how to use it. The Rotax uses carbs with a rubber diaphragm that auto control the mixture, to a point. Somebody figured out there was a fuel savings to be made with additional leaning at altitude, rediscovering the wheel, I know, and marketed the HacMan Leaner for us 912 guys. A hell of a deal for around $200.00. The after market device I have works in conjunction with the auto control. In practice, I use it like "you guys" (Lycoming/Continental pilots) use yours, sort of. Basically, if flying around at or below my 5140' field elevation (I live 1,000' above the valley floor), I don't mess with it. But once up higher and planning to stay there, like a 9K+ flight today to Wyoming, I lean until I get a stumble, then I richen it up "a bit". That's usually about 30 degree according to my EGT, it gets cooler, I usually end up around 1425. If I continue to climb, I'll go through that simple procedure again, each time the fuel flow meter clearly shows the dividend:.4 to .6 minimum LESS fuel flow per hour, substantial, percentage wise, considering we're talking 3.2-3.4 GPH instead of the unleaned 3.7-3.9 GPH.

I have no one flying the Rotax with one of these leaners that I have got together with and compared notes, I'm on my own and pretty much try and take what you guys do and extrapolate it for the Rotax. Apples to oranges though, like my CHT's today were 140 to 160 degrees! One thing I have found however, is if I get her all leaned out real good at 10K or higher, and then zone out and forget all about it and land at 4 or 5K, the engine will quit, right at short final but I had the runway made so no big deal and a great way to educate myself. Another time, after being leaned out just right for 10 to 11K, I landed a 9200' site without re adjusting things. On shut down I got one hell of a loud POP, like I had never gotten before, a backfire. I don't lean for takeoff, I just let the auto control get it close enough, it's just on the long high flights I really find it pays off.

My plugs look great, all the other temps are good, so I'll continue to operate it as is. However, I have not tried going leaner after that initial stumble, that's how you get to lean of peak right? Hope this doesn't confuse your issue Anne, but I feel I can chime in with the others and say that leaning really pays off, however and on whatever, you do it.
 
If you don't lean on take off at elevation you will one day find yourself crappin' your pants an wondering if you're gonna climb out over obstacles - then you realize your error, you lean, and its a whole new airplane. Conversely, if you forget to richen the mixture on descent and arrival, especially at elevation, you may pull power and find you get a surprise deadstick landing. There are those that have and those that will. Ask me how I know this... :)

I know what you mean about leaving for takeoff. It was almost like taking off with the carb heat on. But it wasn't on. Then I remembered something when I was a private pilot about leaning for takeoff. And it was like having my old airplane back.
 
One of the REALLY bad things taught in flight training in lower elevations is that you push "the throttle and mixture" all the way in at the same time on takeoff. I have seen a 180 almost not make it out of Johnson Creek because of this, I flew with the guy afterwards, watched him lean for takeoff during the run up, then push the mixture in with the throttle on takeoff. Years of bad conditioning in his case - probably 30 plus years of it.

sj
 
I do lean at cruise, but not for takeoff or landing. I had one mountain flying lesson many years ago in Phoenix where the DA was pretty high. Even though airport elevation was 1000' MSL, it was hot, and the instructor leaned the engine for takeoff, then we left it there the rest of the lesson. Is that normal procedure in the mountains? Looking at my route westbound, I'll be getting into higher elevation than I'm used to here at 839' MSL.

A good rule of thumb is the lean for take off any time your DA exceeds 5000'. On a hot day, that's going to be at 3500' MSL. Barnstormer posted from a manual "...The mixture should be leaned when 75% power or less is being used." Above 5000' DA with a fixed pitch prop on take off, you can't make more than 75% power. My home airport is at 7200'. I lean as soon as the engine starts. Otherwise I'll have fouled plugs in no time.

Cub Builder
 
Anne,


A little more thread drift already touched on by aktango58.


If you haven’t flown in to high DA airports before you’ll be surprised at how much faster your ground speed is for the same indicated airspeed. And the higher you go the faster it gets. This of course equates to more runway traveled, both landing and taking off.


In your home area you might be used to “intersection departures” and “landing long”. After all in the low, flat lands who needs 6,000 feet to takeoff and land. On the high DA strips, regardless of whether they are in the mountains or not (but especially in the mountains), don’t leave any of the strip behind you - taking off or landing. You might not need the full strip length to take off, but you might need it to gain enough altitude to clear obstacles - like that big piece of granite in front of you ;-).
 
sj and others will remeber their experiances at the 2004 n.m. fly that started at ruidosa,ron masse,paul horney,and i decided early on in planning,that we would start at a lower airport with plenty of runway,mainly for safety of pilots not having high density experiance. alot pulled cowling doors upon landing at their first 6500' runway!! n.m.state aviation on our suggestion held high altitude operations and mountain survival class for flat lander's!! like barnstormer stated don't leave unused strip behind you,this also applies to off airport,even in alaska!!


jr. :)
 
Good reminder on the ground speed! Keep one eye on the airspeed for a while. It will freak you out if not expecting it, having the ground going by twice as fast as you think it should... yet you are almost in a stall:-?

The good part is when you are done you will have your takeoffs down to a science. You will not be able to push power, pull flaps; you will have to keep it strait for a little while before lift off
 
Jr, I think the Bill Tracy will remember that more than anyone! :)

sj
 
Is that true airspeed, or indicated? Should I still be using my normal (gauge) speed on landing?

Anne.
 
Anne,

Yes, use normal approach speed on ASI. Air is less dense, and the ASI is affected by air density. Think of the ASI as counting air molecules to arrive at an airspeed. Less dense air means air molecules farther apart....so probe has to move faster to count the same number of molecules.

i know....a bit over simplified, but......

MTV
 
Would I still use flaps the same as usual?

It sounds like everything is the same inside the plane, just the earth goes by faster. Might be a little disorienting, thinking I'm landing way faster than I'm used to.

Anne.
 
...It sounds like everything is the same inside the plane, just the earth goes by faster...
Yep, that's a good way to look at it.

And of course your engine produces less horsepower because the air is thiner (which means that for a given volume of space there are less oxygen molecules to support combustion which is the reason for leaning the engine).
 
Anne,

Yep still use flaps and everything else...

If you have a portable Garmin GPS use the E6B page and run the Density Altitude, easy help and if you have XM connected it sort of self updates. Also learn to use the terrain page and set yourself a target dot (set in level flight, with a sharpie) on the windshield to visually gauge elevation of clouds and terrain realitive to you.

There is lots of great advice in this thread. As a fellow sealevel dweller I really like George's comment to take note of the mixture knob length, I measure it in cruise before pulling power back to decend to land. Just use your finger as a guage and start there on the next flight but I push it in a smidgen (even though you gaged it at a higher altitude it was at a lower power setting) for take off power if altitude is 4K or better then in climb out and at safe place just push it in anouther smidge (to see what direction you need to go) and then lean for max power by feel and again push it in a smidge for the climb (just like a normal at home leaning) and repeat every 3K feet of climb or so.

Also remember that at altitude and especially in the front of your cub you'll be in the SUN (even if it's cloudy) so just prepare like you're at the beach with hat, sunscreen, sunglasses, and drink more water than normal and oh yea dust of a sectional or two for shade in the skylight (a little blue painters tape will be your friend to hold it up and to seal off those air leaks that you never knew you had)... At Altitude, pay attention to your head, if you're crusing at altitude (and you will be buzzing along at normal above the ground heights but you could easily be at 10K MSL for a couple of hours) and if it hurts, it's telling you it wants more water and light meals and to get lower when you can.

For long XC trips I take a book and and a camp chair. That way you can enjoy the trip by planning some extra time so if it's bumpy beyond your comfort level or the weather isn't happy just stop and turn some pages.

Cub's, the best way to travel...EVER

Kirby

Ps. For a little company key up on 122.75 you'll be supreised how many folks are on the CB channel.
 
Last edited:
Anne, glad you asked the questions: It's the sign of an intelligent, safe aviator. Good advice from all. Since we've drifted into the whole Density Altitude thing, and other factors which affect takeoff and climb performance, a handy training aid for flatlanders is the T.O.P.Comp Takeoff Performance Computer.

This is a shirtpocket-size six-slide nomographic slide rule which takes account of: Temperature, pressure altitude, runway surface (e.g., concrete, turf, mud...), runway slope (ignored in most pilot training), headwind/tailwind, % of gross weight to yield takeoff distance, as well as % Rate of Climb at altitude. You can calibrate it for your aircraft at your homefield using your techniques. It's so easy even I can use it (but as some of you know, I've got a sliderule on my desk to baffle the youngsters...). Because it's an analog tool, this gadget let's you quickly play with different "what-ifs" and to see which parameters have the greatest effect in a given situation. Last I checked, these are ~$24USD from Sporty's.

And back to the airspeed issue, there's a good discussion of angle of attack independent of altitude,and importance of pitch control in the Soaring Handbook (free download from FAA). I'm betting this will be emphasised at your upcoming Women's Soaring Seminar. Out west, the trick can sometimes be figuring out where the true horizon is for reference.

Enjoy the whole trip and seminar, and please give us a trip report.

Thanks. cubscout
 
Would it be too simplistic to say: just let the airplane deal with it (density altude changes) and just fly it like you normally do. You don't keep your eyes glued to the ASI when flaring do you? Rather, you go by feel, I know when I get to sea level that's how I deal with the change, I don't get fixated on the ASI. Sure, leave more room for takeoff and climbout, lean properly, otherwise fly it normal, by feel.
A SE Michigan native here BTW, now a proud 8,9 and 1 10K+ off airport Idahoan! I landed that 10,500' site the exact same way as any other, I sure didn't look at the airspeed and over think it. Have a great trip.
 
Back
Top