Mountain wave - Losing altitude

mandm

mandm

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Sharing an experience yesterday, I was flying over eastern mountainous terrain (mountain tops were not crazy high like out west) and once trimmed out at altitude, I started losing altitude 500-1000’ and I was unable to maintain altitude even when changing propeller pitch full forward and full throttle.

It was slightly concerning, I thought what was wrong? Immediately I looked at nearest airports, direction and distance, and I looked down below for landing options taking into consideration wind direction just in case. Then I checked engine instruments, oil pressure and temp, and fuel flow. Everything was fine. I then talked with ATC who reported mountain waves with updrafts and downdrafts, and even though I took a mountain flying course, it didn’t really click when it was happening. The mountain flying course was more about updrafts and downdrafts close to the peak of mountains but I was quite a few thousand feet above the mountains so that didn’t click as an option.

Interesting flying experience yesterday and also landed with turbulence and low level wind shear +/- 10kts, trying to maintain 90mph, suddenly ISA is 75mph or 110mph. Was a bit much, but a good non eventful experience.
 
Mountain flying courses generally aren’t about wave.

Get your glider rating. ;)
My first encounter with wave was flying a glider in western Maryland…the guys who were familiar with the area said we probably could’ve made it into the flight levels had we been equipped to do so. My student’s fingernails were Smurf Blue by 12,000 feet.
 
Have heard airlines reporting it, needing blocks, >100 mi east of rockies
 
Glad it turned out good for you another flying experience for you.
 
I once saw a satellite photo on The Weather Channel that showed many many lines of clouds running parallel to the Continental Divide, with the whole array extending out for hundreds of miles to the east. It was the most amazing depiction of mountain wave conditions that I have ever seen. I wish I could have gotten screen capture.
 
Glad you are OK. I lost a good friend of mine to mountain wave out west about 20 years ago, FO in a business jet.
 
I took this photo near Bryce Canyon NP. It was a windy day and a fire was burning nearby. The smoke gave a good picture of what the air was doing as it blew over the peaks. 400E52C4-5EB8-4919-BD5A-E1FDDF7AAC2E.jpeg
 
Glad to hear it was a non-event for you.

As you learned by experience, mountain waves can go hundreds of miles beyond the mountains.

When the plane starts descending and nothing you do is slowing down that descent, it can be quite concerning.

Ask me how I know...
 
mandm said:
Sharing an experience yesterday, I was flying over eastern mountainous terrain (mountain tops were not crazy high like out west) and once trimmed out at altitude, I started losing altitude 500-1000’ and I was unable to maintain altitude even when changing propeller pitch full forward and full throttle.

It was slightly concerning, I thought what was wrong? Immediately I looked at nearest airports, direction and distance, and I looked down below for landing options taking into consideration wind direction just in case. Then I checked engine instruments, oil pressure and temp, and fuel flow. Everything was fine. I then talked with ATC who reported mountain waves with updrafts and downdrafts, and even though I took a mountain flying course, it didn’t really click when it was happening. The mountain flying course was more about updrafts and downdrafts close to the peak of mountains but I was quite a few thousand feet above the mountains so that didn’t click as an option.

Interesting flying experience yesterday and also landed with turbulence and low level wind shear +/- 10kts, trying to maintain 90mph, suddenly ISA is 75mph or 110mph. Was a bit much, but a good non eventful experience.
Click to expand...
Mountain wave can be several thousand feet above the mountains as you indicated. The image below is crossing the Rockies. It was very smooth inside those clouds.
JAK_1100 by Jack Silver, on Flickr
 
Mountain wave can impact heavy jets in the mid-30s resulting in airspeed excursions of +-20 knots. Usually a check of PIREPS will give some idea of what to expect.
 
Sugarbush Soaring (Vermont) on a nice day in the fall.

I sometimes fly to the airport in my Cub from the other side of this range. One year I had to divert to a gap further south because I was concerned about how much fuel was getting shaken out of the tank in the rotor.

wave1.jpg
 
We see it fairly regularly here in Eastern Tennessee. Anytime the winds are strong at lower altitudes and cross the ridges generally perpendicular I suspect mountain wave is likely.
 
Many Power pilots don't really appreciate how wave works. The actual wave is often quite smooth, it is the Rotor that is turbluent.
I have been know to uses a Secondary or Tertiary Wave to improve the climb rate of when flying Skydivers.

if you are encountering continuous sink or lift and want to get out of it, especially when flying parallel to the ridge line either move closer or further from the ridge line.ie. change heading.

Brian
CFIIG/ASEL

upload_2022-11-28_14-11-41.png
 
brcase said:
...if you are encountering continuous sink or lift and want to get out of it, especially when flying parallel to the ridge line either move closer or further from the ridge line.ie. change heading....[/ATTACH]
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I had to do that before crossing Tehachapi Pass once. The downdraft was so strong that I turned away from the ridge, found an updraft, and climbed up to 14.5 or 16.5 to cross a 7,000-foot ridge!
 
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MauleSkinner said:
Mountain flying courses generally aren’t about wave.

Get your glider rating. ;)
My first encounter with wave was flying a glider in western Maryland…the guys who were familiar with the area said we probably could’ve made it into the flight levels had we been equipped to do so. My student’s fingernails were Smurf Blue by 12,000 feet.
Click to expand...

I made it to 18,000 in a Grob 102 at Parkersburg, WV a number of years ago at a wave camp. Those who launched earlier got to 21,000
 
There is a sideways U-shaped series of three river valleys in western Washington. Locally, it is called "The Mountain Loop" and consists of the west-flowing North Fork of the Stillaguamish, the south-flowing Sauk, and the west-flowing Lower Skagit. The open end of the U faces west. South to north the "four points" of the U are Arlington (KAWO), Darrington (1S2), Rockport, and Sedro Woolley. You'll also pass Concrete (3W5) on the way around.

The sideways U is about 65 nm long, extending about 25 nm into the Cascades. Foothills climb from sea level to 1500 to 3000 to 6000 MSL. 10k Glacier peak is just to the SW and 10k Mt. Baker is on the N side of the north opening. Check it out on Google Earth (48.391089° -121.931878°).

The south valley (Stillaguamish) is a classic U-shaped glacial scoured valley--flat bottom, meandering river, and steep sides. It's 3-4 nm wide. When the wind blows from generally N-S or S-N. The valley provides a great playground for up and down drafts. Flying up one side of the valley you will encounter a downdraft. Sliding across to the other side provides an updraft. Very fun. Very instructive.

Because of the surrounding mountains north, south, and east, I've encountered turbulence but never a mountain wave. You can get them playing around the leeward sides of Mt. Rainier and Mt. Baker.
 
My friend's last flight, if the link works. Twenty years ago this month. He was co-pilot. Used to be the lead pilot for Key Bank here in Albany, but Key Bank got rid of their planes, so he was flying charters.

https://app.ntsb.gov/pdfgenerator/R...tID=20021115X05473&AKey=1&RType=HTML&IType=FA

Reads to me that they were on the approach to Taos NM, ran into mountain wave, and were too low and without enough energy to get out. From the report and the plate, maybe they were 4k-6k above ground? Guestimating. Maybe if they'd turned one way or another they could've got an updraft, but being on an approach in actual IMC (I believe) and in a small jet, it seems like they didn't realize how bad the situation was until it was too late. This story still bothers me. He was one of the kindest people I've ever met.
 
Palmpilot said:
I had to do that before crossing Tehachapi Pass once. The downdraft was so strong that I turned away from the ridge, found an updraft, and climb up to 14.5 or 16.5 to cross a 7,000-foot ridge!
Click to expand...

I crossed that pass at 10 and felt it on a “light” day.
 
This photo from a pilot who flies Doctors from west of contenental divide to east side ,north Montana.
Said the cloud layer was a mile thick.
 

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farmrjohn said:
I know that standing lenticular clouds are ones to avoid…
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Actually, as Brian indicated, the lenticular, being “part of” the wave are normally quite smooth. It’s the rotor below them (that you might decide to fly through if you were avoiding the clouds) that can be quite rough.
 
We actually experienced what I think was wave last week enroute from Midland to El Paso. We were up about 9500 southeast of Guadalupe Peak and we hit 50+ KT headwinds (groundspeed of 75 while indicating 130!) and there were some places we simply could not maintain altitude.
 
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