Tuesday, July 23, 2013

Flying around mountains

For the most part, every approach I perform is to an airport surrounded by mostly flat land. Every now and then I get to fly around mountains.

Recently I had a trip to and from Colorado.

I'd been to the airport just once before. That time it was my Captains leg. This time it was my leg.

It was a VFR day. The airport elevation is 4858 feet MSL.

The airport was VFR but the the arrival was covered in towering cumulonimbus clouds.


Arriving from the east, ATC vectored us south of the Grand Mesa which peaks at 10920 feet MSL. Once a bit west of Grand Mesa we were cleared to 11000 feet. I picked up the airport and we were cleared for the visual.

I remembered how hard my Captain had to work to get in. I like it easy so I slowed early and began configuring for landing.

Descending through 9000 feet the aircraft was in final landing configuration and I was headed toward the runway.

Due to terrain there is no straight in approach to runway 29. I loaded up the GPS/RNAV approach as a backup to the visual. Being a warm and windy day, the ride was not exactly smooth. A few updrafts and chop as the winds rolled off the terrain.

Right before the approach end of the runway is a fairly deep drop off and a few hills on each side. On the last approach my Captain knew this and prepared by adding a few knots as he lost speed on short final...almost like wind shear.

I briefed and carried an extra 5 knots above V-Approach. V-Approach was set for 143 knots. V-Ref was 133 knots. I was at 148 knots at 500 feet. Sure enough about 200 feet AGL we hit a wind shift causing the nose to rise and airspeed to drop. The speed trend vector quickly went down and the airspeed dropped to 137 knots.

A few flicks of the wrist and the main wheels reunited with the pavement.

Being a fairly high airport and a hot day, the takeoff performance wasn't so great. We were initially weight restricted and would have to leave behind 2 passengers. We looked at the numbers and used the headwind to help increase the climb limit weight enough to get them on.

For each takeoff we have to look at various performance figures. Two of the figures are runway limit and climb limit.

The runway limit weight is set so the aircraft can accelerate to V1, abort and stop safely on the remaining runway surface.

The climb limit weight is set so the aircraft can accelerate to V1, pop an engine, takeoff and clear all terrain while climbing out.

Engineers look at each runway and surrounding terrain to come up with these numbers. They also assign headwind credits and tailwind penalties to the numbers.

Working the numbers isn't hard, just takes time.

The takeoff was uneventful. My Captain briefed the takeoff including which way we would go if we lost an engine.

I've flown to a few airports in Colorado. The most difficult by far was Gunnison as the airport sits at a lofty 7680 MSL. The airport is so high that on high pressure days the pressure altitude could go over 8000 feet. For days when the pressure altitude was over 8000 , there was a restriction in place that I had to wear an oxygen mask for takeoff and landing. Additionally the airport was a "Captains" only airport meaning only Captain could perform the takeoff and landing. When it was my leg we would exchange control of the aircraft prior to arriving or departing. A little odd.....but that was the rule.


  1. Hi there, when you descend thru 9,000 feet does that mean your altitude above sea level ie 9,000-4,858 = 4,142 feet above field elevation?

    Thanks for the post!

    Dave from the UK

  2. Correct. All altitudes are MSL.....above sea level


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