Ewfflyer

I'm with the crowd that's 10 seconds is way too long in most light GA aircraft. That is definitely excessive KE at that point. Not to mention there are just too many factors where you reference your start time, wind conditions, weight, actually being on speed, etc....

rickair7777

Non-technical types tend not to understand KE=1/2MV^2

A few extra knots adds more than a few extra feet to your LDG distance.

PW305

I'm not sure I understand what you mean by 10 seconds of KE after the flare. I couldn't apply that to the Learjet or to any light airplane I fly.

I do bring KE into every training discussion of runway performance and brake energy though

Hawker Driver

Great replies so far guys!

I completely agree with Ewfflyer and the others regarding the comments about ten seconds being way too long to keep any GA airplane, or larger for that matter, flying after a flare. But, that statement was never made......

I was only speaking about the total kinetic energy, 10 seconds, that one will generally have "available" after flaring any airplane at it's appropriate approach speed. What one does, with some or all, of that energy is entirely up to them. Apologies for not making that clarification.

Also, I made sure my own students never landed after a one or two second count, but by a 6 or 7 second count. And, never ever by a 10 second count. The tool enhanced safety and always reduced the amount of flying time my students required to solo an airplane.

My goal, as an instructor, was to provide my students with a superior reference that they could apply first hand than what was out there: Pulling back on a yoke, covering up a runway with a nose or waiting for something close to a stall warning horn to sound just prior to a touchdown. The "old" tools were not providing the correlation my students desperately needed to tie it all together.

Hawker Driver

It's just a rule of thumb.

throttleweenie

So far, a stabilized approach and flaring until it feels about right haven't done me wrong. But that's only about 22,000 hours' worth, so maybe I better dust off the Physics book and rethink this.......REALLY?!?!

TW

Adlerdriver

Something I haven't heard discussed often is power reduction relative to KE.

As a former fighter pilot, the only perspective I brought with me to flying big planes was a heavy fighter needs to land power on or at least with a delayed power reduction into the flare. If you're light, you pull the power sooner.

This is completely opposite to what is required in a transport category jet (especially big ones). The heavier you are, the more KE you have and the sooner you need to pull power to begin to bleed it off. A very light aircraft will need power on (sometimes into the flare) to avoid the bottom dropping out too soon.

It may be obvious to you lifelong heavy drivers but it wasn't a concept to which my previous life gave me any exposure. It really wasn't discussed in training and was something a few "good" Captains were careful to bring up when we were looking at max GW landings or very light ferry operations.

2StgTurbine

I still don't really understand how this is a good rule of thumb. A 6 second flare is not a flare, but a float. Let's take 2 examples.

Example 1, a GA aircraft:

At an approach speed over the runway of 65 KIAS and a touchdown speed of 45 KIAS we will use an average speed of 55 KIAS. After a 6 second flare, you will eat up 555 ft before you even touchdown.

Example 2, a medium size airliner:

At an approach speed over the runway of 135 KIAS and a touchdown speed of 125 KIAS we will use an average speed of 130 KIAS. After a 6 second flare, you will eat up 1310 ft before you even touchdown!

What is wrong with coming over the runway with just enough KE to flare for a second or two?

Hawker Driver

2stgTurbine, nothing wrong at all with flying a plane onto a
runway after a second or two. Kinda required when going onto shorter runways anyway but also the norm at large airports too.

It was wrong of me to make a blanket generalization earlier though.

A while back, I found out the hard way, what really happens when you only have about a second of kinetic energy overall to work with when trying to land in an F18C. Good thing it was just in the simulator. Power all the way to the ground or else. Different for us transport category and little GA guys.

A long time ago, when the dinosaurs still ruled the earth, we all had to demonstrate short field techniques in little airplanes. That was probably the first time most of us had the opportunity to experience, first hand, the limitations that a reduction in kinetic energy bring with it.

A couple of seconds were all you had.......

Not so for transport category jet operators. We still have the same approximate amount of "available" kinetic energy adjusted for weight regardless of where we are landing when we fly by ref. Sometimes though, we just don't have the luxury of time to mess around.

The counting technique I used then, and still use to this day, served an an invaluable tool that assisted my students in correlating the relationship between angle of attack, airspeed, available time and the role kinetic energy plays on every single landing.

Flyhayes

Hawker Driver-
I'm not sure if you mentioned it, from where do you start your count? Is it when you pass directly over the threshold. Are you counting in only the flare or do you start at the round out to the flare? None the less 10 seconds, or even 7 seconds seem way to long to me. I can certainly understand the merit of helping a student judge the flare with the help of a little timing. But timing differ every time the rate increased angle of attack differs in the energy dissipation stage of the landing.