sudden drop over runway

[ebykowsky]

So this may be common, but I've never really experienced it before:
I was landing at night on rwy 35 with winds 120@9 (yes, I know 17 would have been an optimal choice, but it was fairly direct xwind and 17 is NOTAM'd for night landings and more or less out of the question. Anyway, at 1000AGL I was crabbing to adjust for about a 30kt wind and got to experience some decent turbulence on final (ASI was jumping between 60 and 75 as I tried to hold 70). Anyway, over the runway about 4ft high and halfway into the flare still holding 60-65, I suddenly drop pretty quickly and save the landing last second with a hard pull on the yoke. It turned out to be a pretty smooth landing with plenty of runway to spare (total length 4500) but it was probably the most tense landing yet. Is there anything I should be doing to prepare for or anticipate that kind of drop? I think if I hadn't done anything in time there, I would have at the very least put a nice bald spot on the tire, perhaps had a nose wheel landing the way it dropped. So, how should I have handled it differently?

OTOH, I gave my friend his first GA flight ever and he loved it! Did steep turns, showed him why stalls aren't scary, demonstrated a couple of 0g pushovers, and taught him all the science of flight since he's a mech-e major. Even let him fly for a minute or two!

 

[Silvaire]

You've obviously got your hand on the throttle and ready to use it but turbulence can't be seen (even in the day) and there is always going to be a point during the landing when your options are limited because you have to transition from graceful flying machine to squirrely rolling contraption at some point.

My airport is somewhat notorious for winds and turbulence during the summer and one day a student and instructor in a 172 came in, dropped onto the runway and busted the nose gear clean off. Two other instructors then flew over in another 172 from the same flight school to pick the guys up and guess what happened - busted the nose gear off of that one too.

I don't think they've been back again since.

 

[JoeSelch]

...

I don't think they've been back again since.

Is that because they're still there?

(Sorry - just enjoyed your post. Esp the "squirrely rolling contraption" part)

 

[JasonM]

Was there any terrain difference where you experienced the drop? Did you fly over a small valley or anything before the runway? The airports where I am training have river valleys, mountains and drop off terrain that will cause that depending on the wind almost all the time.

 

[ebykowsky]

Was there any terrain difference where you experienced the drop? Did you fly over a small valley or anything before the runway? The airports where I am training have river valleys, mountains and drop off terrain that will cause that depending on the wind almost all the time.

Yeah, the airport sits in a bowl. Final approach to 35 is flown within 1000ft of a mountain to the left (and the mountain is above the glideslope for most of the descent). The turbulence and sudden drops on final weren't much to worry about; I'm pretty certain that the gusty winds coupled with some terrain caused the drop, I am more concerned on how to prevent such a thing in the future.

You can see the terrain on Google Earth if you look up KPJC.

 

[greddawn]

I don't know if this will help you at all, but we have a similar scenario that happens quite often at our runway.

We have a highway and big parking lot about 500 feet off of our primary runway where I fly out of. On warm days, we get one hell of a thermal that will balloon you up 100 feet on short final. As soon as you get over the grass, the bottom drops out.

Although It's fairly easy for me to anticipate, I could imagine it would be scary for a pilot unfamiliar with the airport. We compensate by pulling the power and riding the thermal, then adding a little back as necessary right before the flare.

Moral of the story - don't hesitate to throw power into the flare if you feel like you are losing lift or getting a downdraft.

 

[LifeInverted]

Is there anything I should be doing to prepare for or anticipate that kind of drop?QUOTE]

I think you're doing quite a bit for yourself by anticipating already! Be prepared for what ultimately might not happen, and you won't be caught with your pants down when it does!

 

[bluerooster]

The approach to 34 here at JZP has a small cliff, which causes an area of sinking air as it flows down the runway and over the edge of the cliff.
I found that I can use the sink to my advantage, by comming in just a tad high, and riding the sink back down to the glideslope. But the first time or two it will catch you off gaurd and you'll find yerself dangerously low, without the prompt addition of a burst of power.