High Density Altitude Takeoff Tip

Flaps... more flaps does not equal more lift.

The other day I was at an FBO and I overheard a conversation between two pilots talking about flying to Denver in the summer.  The one pilot who had flew to Denver last summer was relaying his experience.  He was flying a 182 into Front Range Airport and said he had a heck of a time departing, because he couldn't get the plane off the ground.  Finally, after using over 6,000 feet of runway he lifted off was able to just barely get a climb going.

This pilot had stated that he couldn't understand how any aircraft could ever fly in or out of an airport like Leadville since he had so much trouble going to Denver.

I was intrigued by this conversation and decided to introduce myself as a pilot from Colorado and ask some questions.  It turns out the plane was loaded properly, well below gross, the pilot, his wife, and maybe 75-100 pounds of bags.  He had taken off into the wind of 7 kts.  The temp was 95, and that was a factor to the performance, but as I asked more questions the real problem became evident.  This pilot had used 20 degrees of flaps.  His thinking was that more was better, and a short field procedure of 10 degrees should be adapted to high altitude procedure of 20 degrees of flaps.  WRONG!

The reality of the situation is just the opposite.  Generally speaking, the first flap setting usually adds more lift than drag, the second, third or even forth flap settings on most aircraft add more drag than lift.  The better procedure would have been to use no flaps, or at the most use the 10 degree setting.

I explained that the 182 is a very capable machine, he just needed a different procedure.  I also explained that I had flown 150hp 172's to and from Leadville (not in 95 degree temps though).

So what is a good procedure for takeoff from a high altitude airport?  First we'll assume you have evaluated the wind, temp, aircraft performance, weight and balance and have concluded that the attempted takeoff is within the capabilities of the aircraft.

If that's the case then the procedure I like to use is to taxi into position using every available foot of runway, lock the brakes, engine to full power, and flaps in the up position (i'll get to using flaps in a second).  When you're ready for the takeoff run, release the brakes.  Once you get the aircraft in the air keep it close to the ground to use ground effect to accelerate (Ground effect is a reduction in drag caused by being close to the ground in flight).  Once airborne in the ground effect you may want to retract flaps if you had used them as well as landing gear.  As the plane accelerates past Vy then it will handle and climb better than if it were at or below Vy.

As you were doing the takeoff run, if you got to the 1/2 way point of the runway and you're not airborne or close to airborne then you can extend the first setting of flaps.  The benefit of doing this during the takeoff run is that the aircraft will initially accelerate faster without flaps.

Every aircraft is different, this procedure may not be correct for some aircraft, but this will work well for many small single and multi-engine aircraft.

by admin

Safe Mountain Flying

An interesting piece of news reporting from the Denver Post.

A couple days ago the Denver Post printed a story about a Plane Crash near Denver.  The following is an excerpt from that article, which a link to has been provided at the bottom of this post.

"Jay Loar, an Erie resident who was goose hunting in an adjacent field, said he saw the plane circle once earlier in the morning and climb steeply into a "stall" maneuver, wherein the plane's engine stalls on the ascent and comes back on during the swift descent."

Reporting like illustrates the types of myth that are perpetuated by the media, the general public, and even some second rate flight instructors.  I can't even count the number of times a new student was fearful of the engine quitting during a stall because they had heard a story like this before.

Setting the record straight...

A stall is an aerodynamic event where progressively increasing angle of attack (raising the nose) results in seperation of airflow from the top of the wing.  A stall has absolutely nothing to do with the engine.  As another instructor (Sandy Hill) put it... "Birds and Gliders can also stall, but neither have an engine."

Recovery from a stall is as simple as lowering the nose of the aircraft, which decreases the angle of attack of the wing, and returns smooth airflow to the top of the wing to restore lift.

Alpine Flight Training focuses on teaching safe Mountain Flying.  We are based in Eagle Colorado and offer short multi-day courses that focus on what pilots need to know to be safe when flying in the mountains.

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by admin