How hard a landing is very hard in a 747?

[Werner747 107]

Hi everyone,

Okay so...

I generally get greasers in my Queen and I have developed a really good landing technique with her.   That said, for various different reasons my 2 of my last three landings were what I would consider to be dangerously hard landings in the sense that it might need some inspection post flight :-).

The first one was on a flight from FAOR - DGAA where I impacted terra firma at around 410fpm, and then today from FAOR - YPPH landing at 355fpm.   I know that there are rules pertaining to the amount of G's sustained during a landing which is used, but can anyone give me some guidelines please?

Many thanks in advance

 

[Guest]

As long as you don't break my legs (literally) or the passengers' spines, you should be ok. :)

[Chock 17,769]

Autoland systems will normally put an airliner on the deck at a rate of about -100fpm, which is very gentle. Airliners such as the 747 can withstand about -800fpm touchdowns, but that would be a pretty hard landing. Probably something around -250fpm would be a good landing rate, since the object of landing an airliner is to plant it firmly on the ground. If you don't do that, the wheels skip along the tarmac, which wears the tires out quicker, whereas planting it down pretty firmly ensures the wheels don't skid too much and so increase the wear on the tires, which is expensive since airliner tires are incredibly costly. In fact most airlines don't actually own the tires on their aeroplanes, they lease them, and when they are worn they can then be swapped, the old ones being re-grooved (this can be done several times), the re-grooved tires are then resupplied to another user. So, the airlines want their pilots to get the aeroplane down fairly positively, as the tires will end up being swapped less frequently.

[iwebber 207]

34 minutes ago, Chock said:

Autoland systems will normally put an airliner on the deck at a rate of about -100fpm, which is very gentle.

According to my logbook I've done 18 autolands...

According to my chiropractor, all of them were over -100fpm...

In fact, I can only recall 1 autoland that was on the centreline and only 2 that didn't leave us both swearing in shock and awe.

Autolands are designed to get the aircraft down in the touchdown zone, on the runway and so you can use it again; and they're very, very good at it.

They are not, however, smooth, gentle or relaxing.

And doing one in less than 100m vis is terrifying.

But we digress...

For the OP, I'd call them firm, there is more damage to your pride than the aircraft.

Hope this helps,

Ian Webber

[HighBypass 2,339]

Does your replay look like this? :D 

or this?

 

[jrgaz 34]

Almost looked liked the flaps were going to get snapped off!  Ouch!

[Captain Kevin 586]

Speed brakes on the Sikway go on strike or something? Seemed a little delayed in deploying for what looked to be a pretty hard landing.

[CaptainGabe 81]

2 hours ago, HighBypass said:

Does your replay look like this? :D 

or this

 

Ouch. 

[pedrotrindade 335]

2 hours ago, HighBypass said:

Does your replay look like this? :D 

 

"30',20',10', KABUMM...10',20'...10'...!!!"

[mtrainer 136]

Seems to me the speed brakes deployed when there was pressure on the rear struts, but since it bounced, the system may have presumed a go-around and stowed the speed brakes.   Note they came back on again once the back wheels were on the pavement.

I believe the system worked in the manner upon which it was designed.

Mark Trainer

 

[Captain Kevin 586]

25 minutes ago, mtrainer said:

Seems to me the speed brakes deployed when there was pressure on the rear struts, but since it bounced, the system may have presumed a go-around and stowed the speed brakes.   Note they came back on again once the back wheels were on the pavement.

Looked to me like they deployed a second or two after the bounce, then retracted afterwards. I could understand them retracting again after the bounce, but I found it a little unusual that they were late in deploying in the first place.

[JRBarrett 3,048]

21 minutes ago, Captain Kevin said:

Looked to me like they deployed a second or two after the bounce, then retracted afterwards. I could understand them retracting again after the bounce, but I found it a little unusual that they were late in deploying in the first place.

The second deployment was probably done manually. They would not have remained armed for automatic deployment after they retracted following the first bounce.

The pilot was probably a bit distracted after that extremely hard initial touchdown, and may have (understandably) been a little slow to pull the lever until being sure the aircraft was indeed "down"!

[Captain Kevin 586]

29 minutes ago, JRBarrett said:

The second deployment was probably done manually. They would not have remained armed for automatic deployment after they retracted following the first bounce.

The pilot was probably a bit distracted after that extremely hard initial touchdown, and may have (understandably) been a little slow to pull the lever until being sure the aircraft was indeed "down"!

I'm not talking about the second deployment, I'm talking about the first one. Look carefully, you'll see the plane hit the runway the first time, bounce, and then the speed brakes deploy before quickly retracting.

[Werner747 107]

Thank you everyone - and NO, my replays didn't look like that LOL!!! It is pretty amazing the amount of abuse it seems that these birds can take.   I would imagine though that the Silway incident would have warranted a close inspection of the gear and flaps before being cleared for service?   

I usually land at between 80-140 fpm, but I suspect that on both of those occasions I had a bit of sheer on finals.   I use FSGRW so I cannot use the weather radar to detect sheers.   This can get tricky sometimes...

Regards

[Nyxx 6,993]

Grease landing are nice but not good, to cut a long story short around -150 is perfect.

200 - 100 is the perfect range.

Anything below -100 can encounter skidded on all but a hot dry runway.

If you can target 165-135