Mountain Flying

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GPS log of the route: https://mapsengine.google.com/map/view?mid=zq0KWADNCtHE.kc4KSzvCOOcI

Most flight schools/rental places at flat land airports require renters to do a mountain checkout flight before they would let renters take their airplanes into the mountains. Maybe it’s part of their insurance requirements?

The extensiveness of mountain checkouts vary, but usually consist of a couple hours flight into mountains, including landings at a few mountain airports.

Just did mine at the place I rent from! (Sea Land Air at Boundary Bay Airport)

At SLA it’s a 2 hours ground briefing with an instructor, and an ~3 hours dual flight. Our routing was Boundary Bay -> Stave Lake -> Tipella -> Pemberton -> Whistler -> Squamish. Was going to do full stops at Pemberton and Squamish, but was short on time so only did a full stop at Squamish, and a touch-and-go at Pemberton instead.

One of the most scenic flights I have done!

The landing at Squamish also turned out to be one of the most difficult landings I did. We landed on Runway 33, with mountains on the downwind side forcing a narrow circuit, and houses at some distance from the end of the runway with noise abatement procedure forcing an offset final approach.

I dropped full flaps on base (extremely short base), and held pretty aggressive forward slip all the way through final, and still ended up too high and too fast, and had to go around the first time. Second time went better because I was expecting it, but it still required significant slipping. There’s also very little time to stabilize the approach and line up with the runway on short final, once past the houses. Runway is also not particularly long, at 2400 ft.

Apparently tight circuits are the norm at mountain airports because of the terrain, and really requires a lot of thinking ahead to slow the airplane down and descend in time.

No in-flight pictures unfortunately. I almost never take pictures on instruction flights. I like to pay 100% attention on learning as much as I can.

Overall, it’s not quite as difficult as I thought it would be, and the scenery is definitely worth the extra preparation required.

This post will be a reminder to my future self, of all the things I learned, in case I don’t get to do more mountain flying soon, which is quite possible thanks to Vancouver weather.

Weather

  • TCU (towering cumulus) = very bad. Mountains = a lot of mechanical turbulence, and thunderstorms can easily develop.
  • Cloud bases are reported in AGL. Would not fly without at least 5000 ft ceiling (personal), since terrain can rise fast, and mountains make cloud dodging a lot more difficult – also have to worry about not flying into terrain. That said, cloud bases generally don’t change fast in mountainous regions.
  • Wind is a lot more important. Flat land pilots don’t care about wind too much except for take-offs and landings, but in the mountains, if wind blows perpendicular to a ridge, one side will have (potentially strong) updraft, and the other downdraft. Downdrafts can easily exceed typical airplane climb rates. Always be mindful of wind direction, and plan for a downdraft if crossing a ridge (cross at an altitude much higher than peak).
  • Downdrafts often cause clouds.
  • Surface wind near mountains = turbulence. Rule of thumb – >25 kt = no flight (severe turbulence). >20 kt = no non-pilot passengers.

Flight Planning

  • VFR routes are generally good if flying long distances.
  • A lot less airports, most of which unpaved and un-maintained, and many without fuel. Extra fuel reserves = good.
  • Try to select valleys with more features to make navigation easier. Rivers = the best. Highways and power lines also good. Mountains may look easily distinguishable on Google Maps, but will turn out to be much harder from cockpit.
  • Ground based navigation aids will generally not be usable. GPS is probably going to be the only available radio navigation technology, and while it’s usually pretty reliable, it’s still a very good idea to plan for a GPS failure. Eg. Don’t pick a direct route over featureless mountains just because there is GPS.
  • Altitude – higher = more turbulence, but more safety margin if engine fails. Lower = more comfortable.
  • Always be either in valley flying mode or ridge crossing mode. Mixing them up = getting lost really fast.
  • Work out magnetic headings for each leg. VERY IMPORTANT. In mountain flying, if a wrong turn is made, it is extremely easy to convince oneself that what they are seeing match what’s on the map, when they are actually at a different place. See: http://www.youtube.com/watch?feature=player_embedded&v=AyZqTQZqJGU
  • Magnetic headings help tremendously for double checking, and also for determining which valley to turn into at intersections.
  • Don’t try to do a lot of climbing in the mountains. Try to get all the altitude needed before entering mountains. Airplane performance can never be counted on 100% especially on hot days at high altitude, and terrain can rise surprisingly fast.

During the Flight

  • When in doubt, chicken out. Flying from bad weather into good weather is not recommended, but flying from good weather into bad weather is much worse.
  • Always leave the back door open. Always think about how to turn back, and never get into a situation where that’s not possible. For example, crossing a ridge at 500 ft above into strong downdraft can mean it won’t be possible to climb back over the ridge if there are low clouds on the other side of the ridge (often caused by downdrafts, and impossible to see before actually crossing the ridge). Another common one is going into a tight valley where turning around is not possible.
  • Try to fly on one side of the valley (preferably the side with updraft – depends on wind direction, and usually the sunny side if wind is calm), to maximize radius available for 180 degrees turn if it becomes necessary.
  • Slow down when valley gets narrower or conditions become uncertain (but not bad enough to turn back). Turning radius at 70 knots is much much smaller than at 130 kt. Also recommended to use some flaps to decrease stall speed (but not a lot of flaps, because then the airplane would drop like a rock).
  • When crossing a ridge, always approach from 45 degrees. That makes turning back a lot easier if the situation looks less than ideal on the other side.
  • ATC will not be available 99% of the time, since VHF requires line of sight. Give position reports to flight service station through remote communication outlets whenever possible, to reduce the area they have to search if you go missing.
  • Always file flight plans with detailed routes, and follow those routes, otherwise search and rescue will be extremely difficult and unlikely to be successful by the time you starve to death should it become necessary.
  • A canyon turn is a minimum radius turn that is very similar to a steep turn. Slow down to ~90 kt, some flaps, 60 degrees bank, pull hard on the stick. Don’t worry too much about losing or gaining altitude… the important thing is to do the turn without impacting terrain.

Airplane Performance (assuming non-turbo-charged piston engine)

  • Engine performance will be sucky at high altitude (especially past ~10,000 ft). Cruising speed won’t be affected too much, but climb performance will be much worse.
  • Use the same indicated airspeeds as at sea level for Vy, Vx, best glide, recommended approach speed, etc. True airspeeds will be higher, but airplane performance is correlated to IAS not TAS. For example, if approaches are usually flown at 70 kt at sea level, they should still be flown at 70 kt IAS at 8500 ft, but TAS will be closer to 80 kt.
  • Plane will feel very sluggish on take-off from high density altitude airports. That is normal. Expect it and don’t freak out. As long as the runway is long enough according to the AFM/POH at the density altitude on that day with an appropriate safety margin, it will be OK. There was an accident where 2 jet pilots unfamiliar with high altitude ops rejected a takeoff past V1 at a high altitude airport because the airplane performed much worse than they were used to. They crashed it overrunning the runway. Fortunately they both escaped almost unharmed, but the multi-million $s jet was written off. Turned out there was actually nothing wrong with the plane. For the plane I flew (DA-20 C1), takeoff climb rate at sea level is around 1000 fpm, and drops to around 500 fpm at 8000 ft. For a lowered powered airplane like the DA-20 A1-80, it can get to as low as 300 fpm. Most pilots would probably freak out at a 300 fpm (VERY sluggish) climb rate if they weren’t expecting it. A 160 HP C-172 would climb at 390 fpm at 8000 ft according to this random POH I found online. All at standard temperatures. Even worse in the summer.
  • Remember to lean mixture to max power according to airplane manual. At high density altitudes mixture full rich provides significantly less power than at the proper max power mixture setting.

That’s about all I can remember for now!

As an aside, we visited Glacier Air at Squamish, and met Francois, the chief flight instructor there, and got a tour of their place! Cool place and really really nice people.

Turned out Francois was also a test pilot for Diamond, and knew way more about the airplane I was flying than I do. That’s really cool.

Apparently DA-20 C1’s were grounded couple years ago due to engine failures in spins, and he was the test pilot that did the re-certification flights after changes in Diamond’s airworthiness directive (AD) was applied, and he used the plane I was flying (C-GRTJ) for the test flights! Cool-to-know piece of random knowledge.