How hard does a 747 land???
Guest
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Echo Tango
Ooooooooooops
Now you see why I have given up flying aeroplanes. Thanks for spotting that.
Andrew
One day when you fly your 747 (or A3XX?) you will learn about CRM or Cockpit Resource Management which is a buzz phrase for the crew working well together as a TEAM.
What you have just seen above from Echo Tango is an example of PPRune ARM (Academic Resource Management)
Also, Andrew, you will have realised from some of the posts to you here that the WHOLE story about what goes on in a landing is quite complex. My aim in my post was that you should understand the basics of speed and acceleration. No more than that. For the simple formula that I quoted to give the correct result for touchdown G increment it would be necessary that your rate of descent was steady (not changing up or down) as only then would the wing be carrying lift exactly equal to the weight. In a real landing it quite often happens that the aircraft is still reducing its rate of descent AT THE MOMENT IT TOUCHES DOWN. This means lift is more then weight and so there will be a small extra amount of G from that. Also that extra lift will continue to have an effect on things during the time that the undercarriage is compressing. Finally, on a tricycle gear aeroplane, the CG will settle through a greater distance than just the oleo compression if the main wheels hit before the nose. But don’t let all that put you off!
Incidentally, you may have realised that when a bad (heavy) landing happens it is not uncommon that the aircraft survives the first hit, bounces in to the air and breaks when it lands off the bounce. This is connected to the wing lift bit of the story above, after the bounce the crew might (instinctively) push the nose down to reduce the height of the bounce, this dumps a lot of wing lift and leaves the gear very poorly placed on the second hit. It can even be nose wheel first which would be even worse news.
Buzzoff
Aw shucks!
JF
Ooooooooooops
Now you see why I have given up flying aeroplanes. Thanks for spotting that.
Andrew
One day when you fly your 747 (or A3XX?) you will learn about CRM or Cockpit Resource Management which is a buzz phrase for the crew working well together as a TEAM.
What you have just seen above from Echo Tango is an example of PPRune ARM (Academic Resource Management)
Also, Andrew, you will have realised from some of the posts to you here that the WHOLE story about what goes on in a landing is quite complex. My aim in my post was that you should understand the basics of speed and acceleration. No more than that. For the simple formula that I quoted to give the correct result for touchdown G increment it would be necessary that your rate of descent was steady (not changing up or down) as only then would the wing be carrying lift exactly equal to the weight. In a real landing it quite often happens that the aircraft is still reducing its rate of descent AT THE MOMENT IT TOUCHES DOWN. This means lift is more then weight and so there will be a small extra amount of G from that. Also that extra lift will continue to have an effect on things during the time that the undercarriage is compressing. Finally, on a tricycle gear aeroplane, the CG will settle through a greater distance than just the oleo compression if the main wheels hit before the nose. But don’t let all that put you off!
Incidentally, you may have realised that when a bad (heavy) landing happens it is not uncommon that the aircraft survives the first hit, bounces in to the air and breaks when it lands off the bounce. This is connected to the wing lift bit of the story above, after the bounce the crew might (instinctively) push the nose down to reduce the height of the bounce, this dumps a lot of wing lift and leaves the gear very poorly placed on the second hit. It can even be nose wheel first which would be even worse news.
Buzzoff
Aw shucks!
JF
Guest
Posts: n/a
Andrew, with this topic in mind I've kept my eye on the IVSI on the landings/touchdowns of a few captains. I don't fly the 747, but the 737, but in theory the comfort for the pax should be thesame 
. One was on a superday (straight down the runway at 6 knots), which was a natural greaser. The touchdown rate was just under 100'/m (About 75 I think).
Watching it on the more normal landings it was between 200-300'/m.
Just some figures so you can compare them to your touchdown rate, though from a different type.
. One was on a superday (straight down the runway at 6 knots), which was a natural greaser. The touchdown rate was just under 100'/m (About 75 I think).Watching it on the more normal landings it was between 200-300'/m.
Just some figures so you can compare them to your touchdown rate, though from a different type.
Guest
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Thanks Phoenix! That gives a more "ballmark" figure for me. As i've now put my average landing rate down to about 100ft/pm.
You must also remeber that the VSI is a little bit behind in what the aeroplane is actually doing.....
But thanks anyway!
regards, Andrew
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Great Quotes:
"Flying is an unnatural act, probably punishable by God."
"London Heathrow has been described as the only building site to have its own airport."
"A good landing is one you can walk away from. A great landing is one you can still use the plane after."
You must also remeber that the VSI is a little bit behind in what the aeroplane is actually doing.....
But thanks anyway!
regards, Andrew
------------------
Great Quotes:
"Flying is an unnatural act, probably punishable by God."
"London Heathrow has been described as the only building site to have its own airport."
"A good landing is one you can walk away from. A great landing is one you can still use the plane after."
Guest
Posts: n/a
AndrewE, that's so in a pressure VSI, but on the 737 (and most other jets) the VSI is fed from the IRS systems, which give a instantaneous reading. There is extremely little lag (can't remember the figures but it's less than 1/10th of a second I believe) in these instruments.....
Guest
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On my last flight I did a little "research" into this. This data of from 767-300.
First landing was what I would rate as smooth, IVSI reading 160ft/min, after the flight I got the "g" readings from the recorded parameters. Landing G was 1.101, max inflight was 1.284, min inflight was 0.801.
Second landing was HARD. I mean no flare.
IVSI reading 490ft/min. G reading was 1.264, with max inflight 1.264 (the landing) and min inflight 0.582 (some moderate turbulence).
So hopefully this will give you a good idea of what to aim for. But remember, in large jet aircraft the aim is not to "grease" it on, while floating half-way down the runway, but to land in the landing zone, even if this results in a firmer landing.
First landing was what I would rate as smooth, IVSI reading 160ft/min, after the flight I got the "g" readings from the recorded parameters. Landing G was 1.101, max inflight was 1.284, min inflight was 0.801.
Second landing was HARD. I mean no flare.
IVSI reading 490ft/min. G reading was 1.264, with max inflight 1.264 (the landing) and min inflight 0.582 (some moderate turbulence).
So hopefully this will give you a good idea of what to aim for. But remember, in large jet aircraft the aim is not to "grease" it on, while floating half-way down the runway, but to land in the landing zone, even if this results in a firmer landing.
