Landing Longer in Summer

[201er]

I've been noticing myself landing consistently faster lately and burning up more runway. Stronger braking or longer roll outs required. In addition to being a tad rusty and a bit overly cautious keeping the AOA down on final, I've been pondering it over a bit and I think I figured it out. 

Piloting technique, the final approach AOA, the final approach indicated airspeed, gross weight of the airplane, etc are unlikely to have principally changed since winter. The thing that has changed is that it is hot!

The reported density altitude swung from about -2000 to +2000 since winter. Most systems do not account for dew point/humidity so that's almost another +1000ft compared to the dry winter in the NYC area. With a 2% per thousand increase in TAS and a difference in 5000ft density altitude, that's about a 6knot faster touchdown speed. That explains a lot.

An additional factor is the way the winds blow here. We tend to get a pretty consistent westerly wind down the runway in the seasons other than summer. In the summer, light easterly or southwest winds are more frequent. Less groundspeed reduction by headwind.

But even if the winds in summer were the same as in winter, they would still play a lesser role in reducing landing distance because of the higher TAS. A 20 knot headwind for a 50 knot touchdown is 4% more dramatic than for a 56 ktas touchdown.

I'm wondering if the higher ambient temperatures also make the tires and brakes any less effective in summer? Can you think of any other factors? Anecdotal stories about landing distance in summer vs winter?

 

[Yetti]

If you are landing faster, then pilot technique did change.  Or the pilot did not adapt to the landing conditions in the correct way.

[Robert C.]

33 minutes ago, Yetti said:

If you are landing faster, then pilot technique did change.  Or the pilot did not adapt to the landing conditions in the correct way.

@YettiNot necessarily.

Mike is referring to the same airspeed (or AOA) but having a higher ground speed due to the higher density altitude and with that comes longer rollout and braking distance.

@Mike: what I have noticed most this summer is that it has been breezier and more gusty where I've been flying. I end up carrying a bit more airspeed than I should. However, I haven't really noticed the factors you mention that much.

Could the heat over the runway make for more float?

[201er]

5 minutes ago, Robert C. said:

Could the heat over the runway make for more float?

That's an interesting point. Immediately over the runway, it's probably substantially hotter than the ambient temperature when it has been baking in the sun. First off that would lead to the density altitude in ground effect to be even higher and even more TAS. Second, it makes me wonder if there is a localized vertical convection off the radiating runway that further contributes to float?

[Yetti]

There would be about a 5 knot difference based on 4000 feet density altitude.  Winter to summer says the E6B

There would be _(insert headwind/crosswind component)___  increase based on the light summer winds

Texas only has two seasons Summer and February.

 

[RLCarter]

37 minutes ago, Yetti said:

Texas only has two seasons Summer and February.

And February is questionable 

[Danb]

6 hours ago, 201er said:

That's an interesting point. Immediately over the runway, it's probably substantially hotter than the ambient temperature when it has been baking in the sun. First off that would lead to the density altitude in ground effect to be even higher and even more TAS. Second, it makes me wonder if there is a localized vertical convection off the radiating runway that further contributes to float?

Mike I landed in Detroit this afternoon,with my AOA balls on accurate and witnessed the phenomenon mentioned above, I certainly believe the thermals over the hot ground, runway along with choppy air due to same increases out numbers by X, patience is important dealing with a wing that wants to keep flying due to these conditions, my stall horn was screaming while I was a foot above ground for what seemed like an eternity, although the AOA indicator was spot on, another reason the gadget is worthwhile.

[DonMuncy]

5 hours ago, RLCarter said:

And February is questionable 

Maybe in Harlingen.  

[DAVIDWH]

Drag racers use the chute to slow the roll.

Mooney drivers activate speed brakes.

[bradp]

I hear the stall horn chirp more in the summer than I do in the winter with gusts and local/micro convective forces.  The Natural reaction is to carry a bit more  speed. I don't think you'd find a single pilot among us that wouldn't carry a little bit more your speed if stall horn was chirping. The natural tendency is probably part of what you're seeing.

[thinwing]

Hot days ,high elevation ,gusty ,thermals on final ,carrying extra 10 kts to cancel out shear from mountainous terrain...

[RobertGary1]

Could be a combo. You may normally land with a fast IAS due to poor technique or not accounting for lighter weight but don't notice/care in the winter. On top of that your GS will of course be higher for the same IAS with higher density altitude.

 

-Robert

[201er]

3 hours ago, RobertGary1 said:

Could be a combo. You may normally land with a fast IAS due to poor technique or not accounting for lighter weight but don't notice/care in the winter.

Nope. I fly by AOA.

[M016576]

If it's hotter than standard day out, it's a higher density altitude, thus your ground roll will be longer, and your aircraft will perform in accordance with said density altitude, not your indicated altimeter.

hence the "check density altitude" warnings that are mandatory on ATIS when the DA gets significantly higher than actual altitude (I can't remember when those warnings are triggered, but they seem constant in the summers where I'm located).  This is a common thing out in the high desert and/or higher elevation fields.

[carusoam]

See if this list of logic helps...

1) higher DA in the summer...

2) higher physical ground speed occurs to maintain AOA and/or airspeed in the lower density air...

3) using Adjustments in power and AOA, the skilled pilot delivers the plane uniformly each day to the landing zone.

4) The one thing that has changed is the momentum of the plane.

5) with high DA, There will be more momentum to account for while getting the plane slowed and stopped...

6) While in ground effect... Is there a measurable or noticeable difference caused by the high DA...?

7) The one thing I notice this time of year, we have very little wind some days...

8) fall and winter comes with more wind down the runway... always helps with landing distances...

PP thoughts only...

Best regards,

-a-

[Browncbr1]

yea, if it is way hot, then your TAS will be higher due to DA.  your ground speed will be faster as a result.  I also find that my landings are a little less smooth in the summer and I think of it like flying through water in the winter, vs air in the summer... It's just a little more solid feeling in the winter.

[Jim Peace]

Touch and Go practice will cure all this nonsense.......