OK Ashling … I was about to let this go as it appears that for you (and at least several others here) I am wasting my time and yours trying to describe what I’ve been saying; but, ...
Here’s what you said in your post, #45:
Originally Posted by Ashling
You have still not addressed my observation about your definition of the straight and level attitude. In your first post you said.
It is whatever attitude that is the “level flight” attitude for that airplane, in that configuration, and at that airspeed. What airspeed? The airspeed you have upon completing the flare.
If you select that attitude it is too high. Why ?
Remember Boeing ask you to flare 2-3 degrees from your approach attitude.
Take a calm day. 3 degree glide at a constant Vref +5, constant power and landing config. Now we raise the nose 3 degrees (max Boeing recommend) in order to flare and we will have selected the straight and level attitude for that config at Vref +5. However in reality we know the speed will have decreased in the flare so our nose attitude will in reality be too low for straight and level if we only raise it 3 degrees. Boeing assume Vref at the end of the flare so we have lost 5kts of speed which Boeing equates to 1 degree of nose attitude. So if we want the straight and level attitude at the speed at the completion of the flare, as you recommend, we will have to raise the nose by another degree. That will mean we will have raised the nose 4 degrees overall, from the approach attitude, which is too much.
Why is this significant.
a. its nice to get it correct
b. tailstrike. In a 800 the tail bangs at just over 9 degrees oleos extended. Boeing assume a landing attitude of anywhere between 4 and 7 degrees depending on weight, flare etc. So if you flare 4 degrees you may have just over a degree of grace or put another way just over 5kts of grace. Not so much then.
I would appreciate it if you could address this concern over your definition of the attitude.
Cheers
I’ll take your comments from your quoting of my statement: “It is whatever attitude that is the “level flight” attitude for that airplane, in that configuration, and at that airspeed. What airspeed? The airspeed you have upon completing the flare.”
You say “that attitude it is too high,” and then provide the example. A calm day on a 3-degree glide slope, at a constant Vref+5 knots. What information you do not provide is the pitch attitude originally necessary to maintain that situation. As I am sure you are aware, maintaining a 3-degree glide slope does not mean an airplane pitch attitude of 3 degrees. Also, as I’m sure you’re aware, flight inside ground effect is not quite the same as flight outside of ground effect. For example, if you were able to trim the airplane to maintain the glide slope exactly centered and didn’t touch the controls or the power you would see the airplane “flare” itself to some degree upon entering and descending through ground effect. It will not be enough to make a nice landing but it will change the flight path angle at which the airplane will hit the ground. Level flight attitude inside and outside of ground effect are not necessarily the same – and more often than not, “inside” requires less than “outside.”
You say “now we raise the nose 3 degrees in order to flare and we will have selected the straight and level attitude for that configuration at Vref +5.” What is it that makes you believe that if you added 3 degrees to the pitch you were holding on final you would arrive at the level flight attitude for that gross weight, airplane configuration, and a speed of Vref+5 knots? Does Boeing say that? Is that supposed to be a level flight attitude inside of or outside of ground effect? What pitch
were you holding on final?
Without trying to sound terribly offensive or critical, might I suggest that the next time you are on final you check the attitude as you describe it? With landing flaps; moderate gross weight; centered on, trimmed for, and maintaining a 3-degree glide slope; calm day; and at Vref+5 knots … I’ll say that you’ll be between 1.5 and 2.5 degrees of pitch during final. Recall that in one of my earlier posts, I said that with landing flaps, moderate gross weight, initiating the flare at 15 feet above the runway with the airspeed still at Vref+5 knots, depending on when you start throttle reduction and the speed with which you make that reduction, if you bring the nose of the airplane up to what would hold level flight, you would be between 1.1 and 1.2 times Vstall and depending on how aggressive you were with the flare you would likely be between 3 and 10 feet above the runway. At moderate gross weights you would likely be between 4 and 5 degrees of pitch to hold level flight at those airspeeds. Of course, without adding power or increasing pitch you will not be able to maintain level flight – you
will descend. If you were somewhat lighter, you probably would be closer to 4 degrees … heavier, and you would be closer to 6 degrees of pitch -
maybe up to 7 degrees if very heavy, but I would think that would be very unusual – and anything above that, personally, I’d just accept the harder touchdown. If you HOLD that level flight attitude – do not raise the attitude, do not let the nose fall – all the way to touchdown – there is very little chance of you striking the tail and you will have adequate airflow across the vertical stabilizer/rudder to maintain directional control.
You have a lot of control of the descent rate … with both elevator and power controls … and, if you’re only 3 to 5 feet above the runway the use of power will not terribly affect (negatively) the amount of runway you use. My preference is to use power, leaving the pitch at the attitude I’ve selected, primarily because screwing around with pitch attitude that close to the runway is the best way to make something worse out of whatever you have.
One main difference between what you advocate and what I’m advocating is that the amount of pitch added to whatever attitude you had during final is going to be different for each pitch attitude flown on final (affected by whether or not there is a crosswind, tailwind, or headwind). I am advocating level flight attitude at the end of the flare – regardless of what you were doing on final approach. What I’m advocating is not a mechanical response to a set of circumstances. What I’m advocating will require some practice while understanding what is being practiced.
This is because the pilot has to learn to recognize when the airplane is in an attitude from which level flight can be achieved with very little added thrust - the definition of "level flight attitude."
What I’m advocating, at least I believe, will provide you better control of the airplane between the end of the flare and having all three wheels on the runway – and will do so whether you’re dealing with wet, snow covered, or dry runways and whether you’re dealing with headwind, tailwind, or crosswind. I also believe it will give you better control of the airplane if you have to recover from a bounced landing, and it will give you better control if you elect to go around. Why? You will not have to worry about what pitch attitude to hold. You will already have achieved it and will have practiced maintaining it.
As I suggested earlier … don’t take my word for it. Give it a try the next time you’re in the simulator. Deliberately see if you can land the airplane on the tail and see what attitude it takes and how far beyond level flight it really is. Try flying down the length of the runway at a constant airspeed of 1.1 to 1.2 Vstall at a constant altitude of 3 to 5 feet. Try doing it with tailwinds and crosswinds – and make sure they’re pretty stiff crosswinds. Land out of each. Go around from each. Try to bounce the landing. Try it. Don’t take my word for it.