High Density Altitude Operations

[gsxrpilot]

This time next week I plan to be departing KDRO which on a Standard Day sits at 6685 ft.

 

The wife, the dog and I are planning to go to Durango next weekend. As you all know, we fly an M20C. And while fast in cruise for a C, it's climb performance is very average.  With full tanks, we'll be 250 lbs. under gross weight.

 

We've successfully departed E38 at 4514 ft. and KABQ at 5354 ft. Both departures were on very warm days. At both, the density altitude was close to 7000 ft.  I expect KDRO in the summertime will be higher than that.

 

I'll appreciate advice from this group on departure operations at airfields of this altitude in a low powered Mooney.

 

Thanks,

[Oscar Avalle]

I fly out of higher altitude field quite often. My home base is at 5,000 feet with a density altitude of about 6,000 to 7,000. My M20C has a full fuel capacity of 64 gallons. I fly out of the field with my two sons (4 and 6) and sometimes a copilot and full tanks. The runway is about 9,000 feet long, which helps. In my M20C I face two main problems: a) high CHT and b ) lackluster climb capacity. The latter is particularly important when it comes to SIDs... but that is a different story. My procedure:

 

Before take off I put 15 degrees of flaps, lean to best power, using my JPI 830 (EGT) and then I apply power being careful to keep the CHTs in line. During the take off role my AOA is also very helpful. I am attaching two videos I made for entertainment purposes but that show me using my M20C in high altitude fields. Hope it helps.

 

Oscar

 

https://youtu.be/fL8Iro5x3xA

 

 

https://youtu.be/QNJfqyytuwM

[Hank]

I took my wife and a small mountain of luggage from WV to Cody, WY via KRAP to see Mt. Rushmore. Other stops in KY, IA, NE, SD and WY at all hours of the day with no problems. We were closer to gross than you are planning. I was VFR only and right at 200 hours, so COD was as far as I was comfortable going; too many hills for West Yellowstone. But had no trouble with the other hills or afternoon DA.

Have fun! And take lots of pictures.

[bonal]

Should be no problem as long as you have enough runway and you can always leave in the early morning for some cooler air and lower DA.

[kmyfm20s]

KDRO has a long runway with fields around it. To prepare yourself at your home field reduce about an inch of manifold pressure for every 1000' of density altitude difference to what your home field elevation is. This will give you an approximation of the feel and distance of takeoff.

[FoxMike]

Takeoff from should not be a real big problem but here are some tips

 

Lean the engine for peak or slightly rich of peak.  Very important to do it right.  DA will probably 7500- 8500 depending on time of day (be sure to compute it at preflight).  You will not get enough power to hurt the engine operating this way. 

 

Runway 21 is slightly downhill.  Downhill is good but a big wind out of the north is even better so use 3 if winds favor it.

 

Use  usual indicated airspeed for liftoff as you do at lower airports.  You will be going faster.

 

The wing does not lift as well, so after you cleanup initially be climbing only a few hundred feet a minute.  You will use noticeably more runway.

 

Lots more could be said but will suffice for a first time.

[xrs135]

I took off out of Reno (4,415ft) the other day at 88 degrees with 3 full sized adults on board my M20C. You can definitely notice a decrease in performance in ground roll and initial climb. It took a bit more time to accelerate to my climb speed of 120mph, however, once there, we surprisingly maintained 400-500fpm through 10,500ft. I was pleased with that.

[gsxrpilot]

Thanks for all the advice. And the videos are great Oscar. There will be a trip report and pictures after the trip.

[Loogie]

Takeoff from should not be a real big problem but here are some tips

 

Lean the engine for peak or slightly rich of peak.  Very important to do it right.  DA will probably 7500- 8500 depending on time of day (be sure to compute it at preflight).  You will not get enough power to hurt the engine operating this way. 

 

Runway 21 is slightly downhill.  Downhill is good but a big wind out of the north is even better so use 3 if winds favor it.

 

Use  usual indicated airspeed for liftoff as you do at lower airports.  You will be going faster.

 

The wing does not lift as well, so after you cleanup initially be climbing only a few hundred feet a minute.  You will use noticeably more runway.

 

Lots more could be said but will suffice for a first time.

Just curious, how do you lean it ROP during ground ops prior to take off? What is your procedure?

[stevesm20b]

I take off from Big Bear (L35) 6,750 in the summer all the time. DA is over 9,000ft. At gross wt 2450 still manage 400 fpm.

[FoxMike]

Run the engine up to 1800RPM or maybe a little more (try to find an area devoid of rocks).  Pull the mixture control slowly and observe the increase in RPM.  When the RPM starts to drop push the mixture back in a little.  After you do it a few times you will get the idea and be able to do it quickly.  It is hard on the prop but better that than  trying to lean while  on the takeoff roll.  Make sure during the takeoff roll that the engine does not go lean.  On the lean side you get a lot less power.

[Jerry 5TJ]

I've departed South Lake Tahoe at over 8000 density altitude, me and the wife and half tanks. I'm sure glad the lake is flat (obviously) and extends for miles and miles.

Another suggestion--think like a glider pilot when you're in the mountains in your NA Mooney. Above 10,000 it's not rare to get more climb rate from upslope air than from Lycoming.

[jlunseth]

I have a turbo so not the person to advise you on leaning. However, I have flown into or out of quite a few high altitude airports. Most of the western fields have longer runways than what we would see in the flatlands and Durango is no exception. You have 9200 feet. The bigggest thing is to be patient and wait until the plane is ready to fly, don't get anxious and try to force it.

In the mountains there are two fairly important things to do. First, fly airways if you are planning to cross the ridges, even if it means flying out of your way to get to a VOR and pick up the airway. The airway routes have been there a long time and used by many types of aircraft, they have generally been designed to give you the lowest crossing altitude and time to climb. If you cross the ridges direct you may find you don't have enough climb and the winds aloft can push you to the ridge faster than you expected. The other thing, when making a major ridge crossing, is to fly roads. They generally give you a lower altitude and a place to land and find help if you need it.

[midlifeflyer]

This time next week I plan to be departing KDRO which on a Standard Day sits at 6685 ft.

 

The wife, the dog and I are planning to go to Durango next weekend. As you all know, we fly an M20C. And while fast in cruise for a C, it's climb performance is very average.  With full tanks, we'll be 250 lbs. under gross weight.

 

We've successfully departed E38 at 4514 ft. and KABQ at 5354 ft. Both departures were on very warm days. At both, the density altitude was close to 7000 ft.  I expect KDRO in the summertime will be higher than that.

 

I'll appreciate advice from this group on departure operations at airfields of this altitude in a low powered Mooney.

 

Thanks,

 

Yes, KDRO will be significantly higher than that in the summer, especially in the afternoon. You are talking well into the low-to-mid 80's with a resulting density altitude over 9,000'. The good news is, coming from the south and crossing to the west around KABQ, you are not approaching over the highest terrain and the approach and departure path is not too bad.

 

But, what I primarily wondered about reading your question is: One who has flown in and out of these airports, particularly KABQ, will typically have had some high-density-altitude specific instruction. Have you? If not, are you saying you flights in KABQ and E38 were just seat of the pants without a real idea about the techniques used? If that's the case, the best bet is always some mountain training but it would be wise at the very least to have a serious one-on-one discussion rather than a haphazard group of tips that don't really tell the whole story (I note as an example of this, admonition to fly over roads - a good idea in general for possible emergency landing sites, but potentially deadly advice for crossing mountain passes). 

[chrisk]

 (I note as an example of this, admonition to fly over roads - a good idea in general for possible emergency landing sites, but potentially deadly advice for crossing mountain passes). 

 

Why would flying over roads make any difference for crossing a pass?    The training I've had suggests flying over roads is good for an emergency landing: possibly to land on, but also so help can get to you easier.  

 

And if flying to the north of KDRO, then I agree there should be more to the discussion than density altitude.  Winds and mountains are something that should be respected.   Know how to cross ridges, and not fly down the center of a valley.   Know the turning radius of your plane .   And of course, knowing where you are is important, so you don't get trapped.

[jlunseth]

The road thing is pretty simple.  The engineers who designed and built that road did not want to spend any more money cutting down the mountain than they needed to, so the road will follow a low elevation route, a valley, a pass, etc.  If you have an engine failure you will have more height above the ground and more time to get ready for your landing, And there will be a flat surface to land on instead of the side of a mountain or the trees.  And help coming along sooner rather than later. That said, my first choice is the airways.

 

There is a caveat to using roads and passes in mountain flying though.  VFR is far and away best.  You don't want to follow a road or airway into a descending ceiling and suddenly find yourself boxed in, flying into IMC because you cannot turn.  The ASA used to have a piece up about a Bonanza pilot who tried that unsuccessfully.

 

ABQ is not very hard.  Very long runway and no mountains unless you are planning on crossing the Sandias for some reason, and you should not have to do that there are choices to go around.  The ringer in a high altitude, western state departure is that long slow hill at the departure end of the runway, and ABQ is a good example.  ABQ's is west town and is called "Nine Mile Hill" and it will take you a long time to clear it if you simply have little or no climb.  I did that years ago with an uncle in an NA Baron from a ranch strip in Prescott, AZ.  It was more exciting than it needed to be.

 

Quite a few of the western airports are located in the valley basins.  If you look at a sectional of ABQ or DRO you will see what I mean.  Even Taos.  Unless you have some urgent need to go east over the big ridges, north and south of the airport you are not over the rocks, you are over platte land, and if you are VFR you can go find one of those spots and take your time climbing. 

[midlifeflyer]

Why would flying over roads make any difference for crossing a pass?    The training I've had suggests flying over roads is good for an emergency landing: possibly to land on, but also so help can get to you easier.  

 

 

It's related to the FAA's depiction of mountain masses on sectionals. The ) ( on the chart identifies where the road crosses a mountain pass (See the one for Monarch Pass in Colorado as an example), not necessarily the best pace to fly through the pass.

 

I used to have some good examples of each but for a number of reasons it may be the worst place to cross a pass. For a few of them, (1) the road may twist and turn so much through the pass that it would make a terrible emergency landing spot (that's common);  (2) the road is at a very low point with much higher terrain on both sides creating a venturi effect increasing the strength of any winds (also very common) and (3) the road can lead directly to a blind canyon with no ability to climb  or maneuver (there was a fantastic FAA road show on VFR sectionals some years back that showed some very scary examples of this).

 

That's not to say to keep far away from roads. Of course, you want  access to civilization or for rescue in the case of an emergency or precautionary landing, but that doesn't require following the road, just being somewhat nearby.

 

You might be surprised at the mountain training flights I've done where the pilot heads right for the dangerous V between two peaks where the road is, rather than than nice wide, flat area only a few miles to the right or left which gives more options and much less chance of problems.

[chrisk]

It's related to the FAA's depiction of mountain masses on sectionals. The ) ( on the chart identifies where the road crosses a mountain pass (See the one for Monarch Pass in Colorado as an example), not necessarily the best pace to fly through the pass.

 

I see your point.  Yes, following the road is not the most important thing.    I've flown between Pueblo and Montrose a few times.  Typically I would take Poncha Pass and Marshall Pass.   As I recall, both were reasonably wide.   The road below was always a secondary consideration.   Also, the Colorado state aviation map is much better than a sectional.

[carqwik]

Plenty of NA planes fly in and out of DRO.  The mountains don't really start until well north of the airport...and coming from Austin, the most tricky part might be flying around the Santa Fe area.  DRO is a huge strip and easily identified from the air as it sits in a wide open plain....

 

The only issue is to make sure about engine management...don't be full rich on T/O (lean for max power on T/O) or landing, leave as much weight behind that you can when taking off, and depart in the early morning when it's cool.  And fly down the runway in ground effect to build up speed before starting a climb.

[jlunseth]

I see we have someone from Scottsdale. That reminds me of one more thing to say about western flying and that is, you really need to be aware of the temperatures and how your engine cooling will perform in them.  In some of these places it can be 100+ in the shade and even if you can get off the ground your plane is not going to be very happy trying to climb.  It is not just that it will take forever to get off the runway and climb performance will be poor, it is that if your aircraft engine does not have great cooling you will see a lot more CHT's than you would like.  When we picked up my current aircraft from Scottsdale several years ago it was 104 F in the late morning by the time we were able to get going.  We should have waited, the people who had set up the engine in Scottsdale had not done a very good job and we saw some exceptional CHT's in that heat no matter what we tried. 

 

Fly early in the morning.  Besides, in quite a lot of those airports in the Rockies they will have afternoon Tstorms almost every day.  You don't want to be in brewing convection in the mountains.

[kmyfm20s]

I usually land at Animas Park (00C), closer to town, cheaper tiedown fees and fuel. Rental cars can be dropped off at the FBO or cab ride into town.  I land KDRO if there is weather or I'm arriving after sundown.

[midlifeflyer]

I see your point.  Yes, following the road is not the most important thing.    I've flown between Pueblo and Montrose a few times.  Typically I would take Poncha Pass and Marshall Pass.   As I recall, both were reasonably wide.   The road below was always a secondary consideration.   Also, the Colorado state aviation map is much better than a sectional.

It is. The Colorado aviation map has commonly flown passes identified. If nothing else, it helps keep away from the ones known to eat piston airplanes more often.

[Hondo]

Some pointers for mountain flying. 

 

http://www.mountainflying.com/pages/mountain-flying/rule_of_thumb.html

 

Decrease weight.  For the Ovation at 3368, 3100 and 2700 pounds the takeoff speeds are 67, 64 and 60 KIAS respectively.  Going from 3368 to 2700 pounds will reduce takeoff roll by ~ 40%.

 

Wally Moran talks about the effects of runway slope and wind.

 

http://www.pilotworkshop.com/tips/downslope_runway_performance.htm

 

After you have lightened the load, inflated the tires, run the numbers and leaned for best power, would you know when to abort if performance is not as expected?   If the airport has a “1/2” sign and you haven’t attained 70% of your takeoff speed when you reach it, you should abort (AIM Fig 7-5-1).

[midlifeflyer]

 

After you have lightened the load, inflated the tires, run the numbers and leaned for best power, would you know when to abort if performance is not as expected?   If the airport has a “1/2” sign and you haven’t attained 70% of your takeoff speed when you reach it, you should abort (AIM Fig 7-5-1).

 

 

 

Not sure I understand that part. I've never seen an airport with a sign saying "1/2". OTOH, one can always point out a location on the runway that is 1/2 the runway length.

[kmyfm20s]

It would seem impossible not to have greater than 70% of airspeed by the 1/2 way point at KDRO. That would be 47kts at 4600' of used runway, I don't think I would want to be in the air at that point.