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Werner747

How hard a landing is very hard in a 747?

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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

 

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

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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.

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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... :biggrin:

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

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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.

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2 hours ago, HighBypass said:

Does your replay look like this? :D 

 

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

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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

 

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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.

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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"!

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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.

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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

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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

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http://www.boeing.com/commercial/aeromagazine/articles/2014_q4/pdf/AERO_2014q4.pdf

 

Start at Page 15. it tells you all you need to know. Boeing philosophy and policy is to rely on pirep for hard landing reporting. Generally 1.4g to 1.8g vlf is the limit. Anything below 1.4g vlf would mean just the basic check is done. Above 1.4g vlf, generally phase 1a and 1b etc etc.

 

i regularly land in the 300-400 fpm sink rate range. It's hard to land on a needle like runway properly. I'm sure many simmers would land in the 150fpm range if they were to fly the real deal. It's a bit like driving a car in a game, it doesn't compare to driving the real thing.

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As part of the certification process the B747 can be safely landed at 6 feet per second at MGTOW and 10 feet per second at MGLW. 

blaustern

 

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How is this landing fps Measured? As the bottom surface of the wheels touch the tarmac and go to 0 FPM, the seat cushion passenger interface is still at 200 FPM!

The struts contract spreading out the deceleration. It this how much the deceleration  is spread out that you feel. Remember, you never notice the 1800 FPM from altitude.

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7 hours ago, KevinMM said:

How is this landing fps Measured? As the bottom surface of the wheels touch the tarmac and go to 0 FPM, the seat cushion passenger interface is still at 200 FPM!

The struts contract spreading out the deceleration. It this how much the deceleration  is spread out that you feel. Remember, you never notice the 1800 FPM from altitude.

Vertical speed (from memory) comes from accelerometers around the aircraft and its data is sent to the computers.

What is a seat cushion passenger interface?

No, you do not generally notice sink or climb rate once this rate is established, you do however feel the changes. If you go from 1800fpm sink rate to 2500fpm sink rate suddenly without compensating for the change in g, you'd feel it. Same for when the aircraft roll's, you feel the changes.

As a further note, students should NEVER put achieving a "greaser" above landing in the touchdown zone with normal attitude.

There are so many YouTube videos, so so many, where this is not done. The students realise that they need to get 150fpm, for whatever reason, and risk tail strike by using abnormally high nose up pitch with a flare that extends beyond the touchdown zone. This would have to be my biggest criticism of all the videos on YouTube.

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What I normally do is use the proper approach speed, and at 20 feet go to idle and raise the nose just a degree or two.   That results in excellent landings, however, as I said I think I hit some sheer on those last ones.   I am seriously contemplating getting ASN to avoid getting caught out by those nasty sheer buggers on finals!

Regards

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You know what they say. A good landing is one you can walk away from. A great landing is one where you can reuse the airplane afterwards.

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A more practical way to determine if the landing was a bit firm without becoming overly involved in "sink rates", etc. is to open the cockpit door.  If all the" carry on trash" has fallen out of the overhead bins is laying in the aisle and the stew is standing there with her panties around her ankles inquiring, "who made THAT one?" then, yes, it probably wasn't a greaser! 

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3 minutes ago, Quink said:

stew is standing there with her panties around her ankles

That can happen?

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Quote

stew is standing there with her panties around her ankles

Anything's possible Kevin. Depends on the almighty sink rate!  The overall effect would be very slow and hostile service to the cockpit for the rest of the trip...........

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