Jump to content

Recommended Posts

Posted

When preparing for take off at high elevation, or high DA, what method do you use? I have spend nearly all of my 14 years of flying at, or near sea level. I have been trying the target EGT method, but I'm unclear the detailed, blow by blow actions. Do you go to the run up and hold the brakes, go full power and adjust the mixture to the target? Do you do it on the runway and not the run up? If this is correct, how long do you sit there full power to be satisfied the engine is stabilized? Is there a better method?

 

I really, really wish the guys like Mike Busch, or those guys from APS would start doing actual cockpit videos instead of just simple (to them) written descriptions of their procedures. It seems that now a days with everybody taping cameras everywhere just for shits n' giggles, somebody could actually use this tech for educational purposes.

Posted

I lean heavily on the ground to avoid fouled plugs.

For runup, I twist the mixture in 2 rotations and watch the EGT during the 2000rpm runup, making sure I'm not above 1250egt.

I then take the active and go full throttle. Watch the EGTs as I'm rolling and make an adjustment so that at full throttle, 2700rpm I see 1250egt. Easy as that. I do NOT hold the brakes at full power to adjust- not enough cooling air through the cowling.

That's my technique which has worked for me operating out of a 4100' msl runway. The highest runways I've operated out of are mammoth (7100) and Sun Valley (5300). This method works there too- just don't let your EGT climb over 1300.

Edit: all the runways I've described and typically operate out of at high altitudes / high DA's, are longer that 5000'. Short or unprepared runways are a different beast. Some guys fly their mooneys out of dirt strips, short runways in the mountains. I do not.

Posted

Dave,

I am providing this only as a conversation piece - check the Airplane Flying Handbook or equivalent for an official position before flying. Also, I highly recommend to take an instructor pilot who has experience in your make and model and in the mountains, before trying this on your own - I actually take instructors with me all of the time. About a year ago, I took an instructor to Truckee Tahoe, and was a bit dismayed to find out that he knew less than I did about mountain flying. So choose wisely.

That being said, I have some experience flying underpowered aircraft out of high airports (Big Bear in a Piper Cherokee, and recently Truckee Tahoe in my M20G). Before we even talk about leaning - let me start with a little low-tech advice. Do not take off after 8 am. Period. Do all of you flying to have landed by 10 am, and do not launch there-after. DO NOT TAKE OFF IN THE AFTERNOON FROM A MOUNTAIN AIRPORT. High DAs are likely, and downdrafts are often more of an issue in the afternoons. If your plane can only climb at 200 FPM, and there is a 400 FPM downdraft, you will be in an uncommanded descent at Vx.

Next, make sure that you have only the fuel you need, plus FAA minimums (In my aircraft, I add a little padding to the minimums - one additional hour of fuel - 10 gallons). 20 extra gallons of fuel is 120 unnecessary extra pounds, which will decrease your climb-rate. Finally, get rid of any additional junk in your plane to reduce weight.

Call the field, and ask about local patterns and no-wind runways. It is very difficult to really understand what it will look like to launch toward a huge mountain like in Truckee Tahoe. Listen to locals advice on how to operate at the field.

Okay - on to the question at hand. Have you ever considered trying to lean while flying in pattern altitude, or at an equivalent altitude of the field elevation while airborne? I lean for peak EGT, and the enrichen between 25 and 50 degrees. Given the low manifold pressures that you are dealing with, you could probably lean simply for peak (which equates to max RPM), but I always enrichen just a smidge for a little protection from detonation. Now remember the position of your mixture control, and use that on the ground. Also, when you lean for peak EGT or max RPM, note your climb rate. That is what you will climb at when you take off from the field, given similar temperature and wind conditions. If nothing else, it is a good reference point.

Others have told me to use 2000 RPM, and then lean to peak EGT - this is a method, but I prefer to lean at field elevation while flying to my destination, and then use that position of the mixture control, again, with 25-50 degrees EGT rich. Yet others recommend to lean in the roll to avoid overheating the engine. I don't recommend this technique unless you have some experience with it. Needless to say, you probably will adjust the mixture a bit even after you have taken off to ensure max power.

In the end, the whole idea behind leaning is that with the prop full forward, maximum manifold pressure and maximum RPM equate to maximum power. With the prop at 2000 RPM (on the ground), you will adjust mixture until you see a max increase in RPM. In flight, I use peak EGT to equate to max power. If you think you aren't getting maximum power, by all means, adjust the mixture a bit. But I have found that as important as this is simply avoiding bad situations by only operating in the mornings, by only taking the weight that I need, by talking to locals, and by making no-go decisions more often than I care to own-up to. :)

Hope this helps.

Sean

Posted

My airport is at 5880'. There is a digital Density Altitude sign where you enter 17L. I have seen 8880' on that sign. With 10,000' of runway leaning is not a big distraction rolling. That said:

 The knob is out about an inch all the time. If it were all the way in the plugs would foul. My egt is calibrated in Centigrade. I dont like to run full power and set the mixture standing still. Too much dirt through the prop. So 675c/1247f is what I look for initially. Any thing 650 to700 is safe to take off. Once cleaned up in the climb set as needed.

Posted

Sean posted some good mountain flying advice along with incorrect engine leaning advice.  Peak EGT =/= max power, and you can't lean to max RPM with a constant speed prop like we have on our Mooneys.  Leaning to 25-50 dF ROP is also the worst advice for leaning, period.  We've gone thru that many times on this site so need to repeat it again.

 

The Target EGT method is the simplest, safest, and most effective for our non-turbo Mooneys.  You should have an idea where the mixture knob should be by making a mental note of it's position prior to landing.  If you're one of those that enrichens for landing (I don't!) you should only enrichen to the Target EGT if you're landing at high DA.  Note the position!  When you go to takeoff, put the knob in that position as best as you can remember, and while you're rolling down the runway fine-tune it to reach or maintain your Target EGT.  It is that simple.  Your takeoff roll will be much longer at high DA, so you have plenty of time to make an adjustment or two before lifting off.  There is no harm in holding the brakes and setting your takeoff power UNLESS you're on an unimproved strip with a lot of FOD, but keep in mind you'll be generating more MP while moving due to increased mass air flow going into the induction system, so if you hold brakes and set the mixture, you'll have to tweak it again when rolling and flying.

Posted
  On 1/16/2013 at 10:30 AM, NotarPilot said:
Anyone here care to comment and explain the "Big mixture pull?"

 

I always associate this with Mike Busch's comments on leaning for LOP operations. It's his approach for quickly leaning past peak EGT so as to avoid the "red box" or "red fin" or whatever other imagery you want to use that denotes the area where detonation is possible. With this approach, you lean quickly to the far side of LOP, then enrich mixture until you see the temps you want. 

Posted

Jeff is correct... once you've figured out your LOP power settings, you can simply pull the mixture fairly quickly to that general area, and then fine tune.  No need to very slowly lean through the "red box" to find peak and then lean some more...just get past peak in one swift pull and then fine tune to your target fuel flow, or enrichen back to peak and then re-lean from there.

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.