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Thermals on landing

N

NewbRVator

Well Known Member
Anyone ever encounter a thermal over the runway during a landing?

Just wondering. I was landing on a freshly paved black asphalt covered runway and the weather is starting to heat up here in Central California. As I came in over a water feature, trees, and grass the transition to the runway is abrupt. At about 5 ft over the runway I had a pretty good burble. At first I thought crosswind but after landing safely I think it was a thermal off the asphalt.
 
Sure, especially in the valley; always bumping around like crazy out there. We have a somewhat consistent sink over a pond at the approach end of KPAO 31; some days it's particularly strong. Also, at KHAF, if you're flying the rare 12 approach, the winds over the costal bluffs will give way to a good shear and noticeable loss of lift ... at 200'.

Every airport has its special character; some of the more scary ones only show up rarely.

Each landing is like a snowflake!
 
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Thanks for the thoughtful replies. Always good to review the basics and bounce experiences off others. Cheers
 
A good pilot will always adapt to the situation. Flying is a skill, a skill that you never stop learning :) In 40 years I'm still learning everytime I fly 👍
 
Floating Flare

Solo flight training at KBED with snowbanks next to the runway. On a warm, clear spring day with a quartering 4kt tailwind I floated with rocking wings for what seemed like forever in, as I later realized, cool air from the snowbank drifting across the runway and lifting. It was noticeable enough that the tower commented in their next call to me.
 
We had a Rans 7 that more than once we would gain altitude while on base,power off, nose pointed down,full flaps,at max flap speed.
 
eric.the.blonde said:
Solo flight training at KBED with snowbanks next to the runway. On a warm, clear spring day with a quartering 4kt tailwind I floated with rocking wings for what seemed like forever in, as I later realized, cool air from the snowbank drifting across the runway and lifting. It was noticeable enough that the tower commented in their next call to me.
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(Bold added by me )

You didn't say what kind of airplane you were doing training in, but if you were in a Cessna, the landing distance chart adds 10% for every 2 kts of tailwind.
 
Years ago I had an L-39. Did airshows. Part of my routine was a very high speed very low pass over the runway. Thermal bumps could be so intense it felt like my fillings were coming loose. Just part of the excitement.
 
Desert Rat said:
(Bold added by me )

You didn't say what kind of airplane you were doing training in, but if you were in a Cessna, the landing distance chart adds 10% for every 2 kts of tailwind.
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Since aircraft fly through the air, for a given amount of energy the flare will take the same amount of TIME all else being equal. All that chart tells you is that you'll consume more runway with a tailwind -- true of any aircraft.

I'm sorry my example did not clearly specify that the flare took more time than expected.
 
wjb said:
Sure, especially in the valley; always bumping around like crazy out there. We have a somewhat consistent sink over a pond at the approach end of KPAO 31; some days it's particularly strong.
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Yep, I learned to fly at PAO and I'll always remember the sink over the pond. Of course, back then, the runway was 30... the planet has changed a lot since then. ;)
 
NewbRVator said:
Anyone ever encounter a thermal over the runway during a landing?

Just wondering. I was landing on a freshly paved black asphalt covered runway and the weather is starting to heat up here in Central California. As I came in over a water feature, trees, and grass the transition to the runway is abrupt. At about 5 ft over the runway I had a pretty good burble. At first I thought crosswind but after landing safely I think it was a thermal off the asphalt.
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Extremely common. Sink rate and thermals live in close proximity. what goes up must come down and air flow trades direction and position in near proximity. From my soaring background this is a big consideration because glider guys and gals have to manage energy, time and environment in ways that lead to more importance for the "setup" and assertively maintaining SA and managing an arrival since the "go around" is not an option.

Wind and air parcel movement in a horizontal movement may also vary drastically between 50 feet above the surface and on the surface in some locations (also dependent upon surface features, terrain variability and solar effects). This is called Wind Gradient. This is especially important to consider when flying aircraft with generally lower stall speeds and lighter weights (yes our RV's). This is because the the kinetic change in air flow and the aircraft moving within the transition gradient is greater by percentage of stall speed and mass.

In mountain airports with local terrain and surface composition features in the right combination - those may at times sport heavy sink and heavy thermal bumps in close proximity leading to, for example, sink on short final and then lift over the threshold. Or, vice versa. add wind gradient and surface turbulence down stream of other features and you have a handful to enjoy. Being ready to go around is always a good option to exercise when in doubt in our RV's. Also being ready to go to another airport is typically always a good option to have in one's back pocket too.
 
Sure, if the "cowbell" comes with more stick time and "learning stuff", then yeah, ok. It all starts making sense soon enough :)
 
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Sounds like you want a little less cowbell and little more stick. That SNL skit was classic. As for thermals I like the responses. I am learning tons here. Thanks!!!
 
?I got a fever!? Agree, it?s a classic skit. If Cowbell = Straight Runway Alignment on touchdown and roll out, then Cowbell is a good thing. Ring that bell!
 
I?m honestly curious where you learned to fly that you didn?t experience thermals landing as a student? I?ve flown a lot of the country now, more big ?shiny? jet but even then there?s not one place that there wasn?t a good sinker short short final. Or opposite going from cool air of say crops or pond to the hot tarmac.

Admittedly I couldn?t see this stuff until the last couple years until it happened, now that I have started taking up glider flying I know what to look for a lot better.
 
A little humor here, true nothing rings my bell as to land on a hot day on black asphalt. So one day I was landing in a small airport in Ohio. I lined up for final, and just before the end of the runway , I switched to the left and landed on the green. Wow! what a landing, smooth as silk. Cessna 170 BTW.:)
 
tgibbs said:
I?m honestly curious where you learned to fly that you didn?t experience thermals landing as a student? I?ve flown a lot of the country now, more big ?shiny? jet but even then there?s not one place that there wasn?t a good sinker short short final. Or opposite going from cool air of say crops or pond to the hot tarmac.

Admittedly I couldn?t see this stuff until the last couple years until it happened, now that I have started taking up glider flying I know what to look for a lot better.
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I don't remember thermals on landing when I got my private over the winter of '64/65 at the old Phillips Field in Fairbanks, AK. But, I don't remember much of anything from that long ago except it was cold. And dark.
 
sandpiper said:
I don't remember thermals on landing when I got my private over the winter of '64/65 at the old Phillips Field in Fairbanks, AK. But, I don't remember much of anything from that long ago except it was cold. And dark.
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Fair enough! I haven?t been to Alaska yet, that would be a neat trip for sure
 
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