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Singapore Airlines Turbulence Problem

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degsy said:
'Clear air' turbulence - the plane drops - you effectively stay where you are - and hit the ceiling with a wallop

Keep your seatbelt on?
Click to expand...
Happened to me going into Singapore 1991 , on the way to Australia.
We were going through a storm and just dropped.
I had my seatbelt on luckily , but what a wallop to the guts .
Everything hit the ceiling, drinks ect, I started laughing at the time because some poor woman had been on the toilet and obviously the water in the pan must have splashed her.
The look on her face , legs wide open walking back absolutely soaking.
Wasn't so funny afterwards because I got a fear of flying only getting over it the last year or two.
Don't mind the actual flight but absolutely hate having to have the seatbelt on makes me have anxiety.
 
PhilM said:
While it wasn't this severe, I flew into Vienna once through some major turbulence, and it was pretty nauseating and very, very unsettling.

On our final descent, I remember at one point looking out the window (obviously sideways looking) and saw the runway running almost perpendicular to the plane.

"Shouldn't that be in front of us?" went through my mind, I'm not ashamed to say I did a few Hail Marys at that point.
Click to expand...
Standard crosswind technique Known as the "Crabbed Approach"

Ideally, runways are aligned into the direction of the wind. It makes take off and landing easier since there's no sidewards component of wind to deal with, and safer since it uses less runway....In reality of course, the wind strength and direction are variable, so we have to have well rehearsed methods for crosswind approaches and landings. The technique that most aircraft use when making an approach with a sideways component to the wind (a cross wind) is the crabbed approach. Think of it as trying to swim across a fast flowing river to your mate who is directly opposite you on the far bank....If you aimed straight towards him you would be carried downstream by the flow, and not arrive where you intended. To be able to track directly towards your mate, you would have to aim upstream enough so that the sideways movement from the flowing river is cancelled out. Its basically a triangle of velocities with the resultant vector being in the direction you want.

Aeroplanes are just the same, they have to aim into the wind. If they aimed straight for the runway threshold then they would be blown downwind of the centerline and miss the runway. Relative to a stationary observer on the ground, the aeroplane would be flying through the air diagonally (like a crab), and perhaps to a passenger in sight of the runway out of a side window it may appear the same, however the aeroplane is flying very much straight through the air...its just that the air itself is moving relative to the ground!

The problem with this however is the eventual touchdown. Aeroplanes are designed to land on their main wheels which (for all bar one or two rare military types) are non castoring. They are VERY strong and capable of absorbing massive compressive forces, but what they don't like are side loads. The crabbed approach with it's nose offset orientation would load up those main wheels with side loads if touching down without straightening up first. This is all done at the last second when the aircraft rounds out just above the runway by using enough rudder to align the nose (and wheels) with the runway, and applying opposite roll control to maintain wings level. Very satisfying when done correctly!
 
slipstream86 said:
Standard crosswind technique Known as the "Crabbed Approach"

Ideally, runways are aligned into the direction of the wind. It makes take off and landing easier since there's no sidewards component of wind to deal with, and safer since it uses less runway....In reality of course, the wind strength and direction are variable, so we have to have well rehearsed methods for crosswind approaches and landings. The technique that most aircraft use when making an approach with a sideways component to the wind (a cross wind) is the crabbed approach. Think of it as trying to swim across a fast flowing river to your mate who is directly opposite you on the far bank....If you aimed straight towards him you would be carried downstream by the flow, and not arrive where you intended. To be able to track directly towards your mate, you would have to aim upstream enough so that the sideways movement from the flowing river is cancelled out. Its basically a triangle of velocities with the resultant vector being in the direction you want.

Aeroplanes are just the same, they have to aim into the wind. If they aimed straight for the runway threshold then they would be blown downwind of the centerline and miss the runway. Relative to a stationary observer on the ground, the aeroplane would be flying through the air diagonally (like a crab), and perhaps to a passenger in sight of the runway out of a side window it may appear the same, however the aeroplane is flying very much straight through the air...its just that the air itself is moving relative to the ground!

The problem with this however is the eventual touchdown. Aeroplanes are designed to land on their main wheels which (for all bar one or two rare military types) are non castoring. They are VERY strong and capable of absorbing massive compressive forces, but what they don't like are side loads. The crabbed approach with it's nose offset orientation would load up those main wheels with side loads if touching down without straightening up first. This is all done at the last second when the aircraft rounds out just above the runway by using enough rudder to align the nose (and wheels) with the runway, and applying opposite roll control to maintain wings level. Very satisfying when done correctly!
Click to expand...

At least one large airplane is designed to crab on purpose. Don’t know which/why/how?
 

slipstream86 said:
Standard crosswind technique Known as the "Crabbed Approach"

Ideally, runways are aligned into the direction of the wind. It makes take off and landing easier since there's no sidewards component of wind to deal with, and safer since it uses less runway....In reality of course, the wind strength and direction are variable, so we have to have well rehearsed methods for crosswind approaches and landings. The technique that most aircraft use when making an approach with a sideways component to the wind (a cross wind) is the crabbed approach. Think of it as trying to swim across a fast flowing river to your mate who is directly opposite you on the far bank....If you aimed straight towards him you would be carried downstream by the flow, and not arrive where you intended. To be able to track directly towards your mate, you would have to aim upstream enough so that the sideways movement from the flowing river is cancelled out. Its basically a triangle of velocities with the resultant vector being in the direction you want.

Aeroplanes are just the same, they have to aim into the wind. If they aimed straight for the runway threshold then they would be blown downwind of the centerline and miss the runway. Relative to a stationary observer on the ground, the aeroplane would be flying through the air diagonally (like a crab), and perhaps to a passenger in sight of the runway out of a side window it may appear the same, however the aeroplane is flying very much straight through the air...its just that the air itself is moving relative to the ground!

The problem with this however is the eventual touchdown. Aeroplanes are designed to land on their main wheels which (for all bar one or two rare military types) are non castoring. They are VERY strong and capable of absorbing massive compressive forces, but what they don't like are side loads. The crabbed approach with it's nose offset orientation would load up those main wheels with side loads if touching down without straightening up first. This is all done at the last second when the aircraft rounds out just above the runway by using enough rudder to align the nose (and wheels) with the runway, and applying opposite roll control to maintain wings level. Very satisfying when done correctly!
Click to expand...
Example...sort of.

 
SerenityNigh said:
At least one large airplane is designed to crab on purpose. Don’t know which/why/how?
Click to expand...
Well the crabbed approach is crabbing by intention. The usual landing technique for most types is to “de-crab in the flare” just before touchdown. Like you say there are some big military aircraft that can control the alignment of the main wheels - the B52, that then lets them land without ever needing to straighten up.

Other big commercial aircraft that intentionally land whilst maintaining some crab - it can be one of the recommended techniques used when the the x wind is very strong and the runway is very wet so the tyres won’t gain as much traction when touching down sideways which allows the pilot to straighten up quickly without being thrown sideways off the runway. It’s not very nice for passengers as they get the sudden twisting jolt when touching down. Like in the posted A380 video.

The decrabbing is tricky when the crosswind is strong. The amount of rudder needed to align with the runway causes a secondary effect of the wings rolling in the downwind direction unless sufficient opposite roll control is applied. If not coordinated correctly then it’s possible to scrape a wingtip or the bottom of the engine pod on the ground (tea without biscuits with the boss). On some types maintaining some crab in the touchdown may help with this….but it’s not very elegant.
 
slipstream86 said:
Well the crabbed approach is crabbing by intention. The usual landing technique for most types is to “de-crab in the flare” just before touchdown. Like you say there are some big military aircraft that can control the alignment of the main wheels - the B52, that then lets them land without ever needing to straighten up.
Click to expand...

Just now realizing my typo in the previous post, but yes the Buff is the only one I'm aware of that turns the wheels. Feel a little like a goon having learned and taught sideslip if everyone crabs landings in big airplanes, but I guess that's how it goes. You learn to handle and prevent damage appropriate to the aircraft, whether it's the main gear on a 172 or the pods and tips on an Airbus.
 
Exeter_Gently said:
Had a terrible experience coming back from Mexico a couple of days after Katrina hit New Orleans...affected me ever since.

My old man worked at British aerospace for years building wings for jumbo's and even his reassurances haven't worked.
Click to expand...

I've worked for BAE the last 12 odd years as a Cat C Engineer; I assume he was working near Preston?

My job largely revolves around EASA legislation/enactment and enforcement of correct practices now so I'm a bit rusty on Bernoulli's Principle etc but the likes of @Mutzo Nutzo and @PhilM regularly blow my mind with the depth of their knowledge in which, I assume, isn't their normal area of expertise.

Clever lads.
 

Tommy. said:
I've worked for BAE the last 12 odd years as a Cat C Engineer; I assume he was working near Preston?

My job largely revolves around EASA legislation/enactment and enforcement of correct practices now so I'm a bit rusty on Bernoulli's Principle etc but the likes of @Mutzo Nutzo and @PhilM regularly blow my mind with the depth of their knowledge in which, I assume, isn't their normal area of expertise.

Clever lads.
Click to expand...
This was the back end of the 80s he started at BAE....he was based just outside London. I'll have to get the full run down off him,hates talking about it because he's broke his leg playing Footy and it effectively finished him there.

One thing I do know he's lives well off his pension from there.
 
edge said:
Happened to me going into Singapore 1991 , on the way to Australia.
We were going through a storm and just dropped.
I had my seatbelt on luckily , but what a wallop to the guts .
Everything hit the ceiling, drinks ect, I started laughing at the time because some poor woman had been on the toilet and obviously the water in the pan must have splashed her.
The look on her face , legs wide open walking back absolutely soaking.
Wasn't so funny afterwards because I got a fear of flying only getting over it the last year or two.
Don't mind the actual flight but absolutely hate having to have the seatbelt on makes me have anxiety.
Click to expand...
The poop went back in such was the force of the sudden drop, hence the legs wide open walk.
 
About 15 years ago I was on pretty much the last plane to land at Osaka before they shut the airport because of a typhoon. The last hour of the flight was just ridiculous. People praying on the plane, genuinely frightening. As soon as you thought it had calmed, a massive drop and screams all over again.
 

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