Passenger on A 747

[a1]

I need people who have flown on a 747 to answer this.


I have heard that as a 747 takes off the passengers fell jerks as if the plane is revving up by levels. An example is a car going 20MPH and then accelerates to 40MPH and back to 20MPH. I don't know if this is true. I don't think people inside would feel jerks but I have never been on a 747 so how should I know.

[beaky]

:-?  :-?  :-?
Never flown on a 747, but I can't see why it would do this. Maybe you heard this from people who flew on a 747 that took off from a runway with raised centerline lights, and felt the bumping as the nosewheel rolled over them, or...?

That's definitely a weird one; there is no logical reason why any airliner would be designed to not accelerate smoothly.

[expat]

:-?  :-?  :-?
Never flown on a 747, but I can't see why it would do this. Maybe you heard this from people who flew on a 747 that took off from a runway with raised centerline lights, and felt the bumping as the nosewheel rolled over them, or...?

That's definitely a weird one; there is no logical reason why any airliner would be designed to not accelerate smoothly.

Never experienced that on a 747 or any aircraft come to that.

Matt

[a1]

One of my theories suggest that the g-forces upon takeoff simulate that kind of affect. I don't know.

[Xyn_Air]

Only flew on a 747 once (about a month or so ago) and did not notice any such jerking during takeoff.  Of course, I have only been on a 747 once, so that is hardly a representative sample of takeoff experiences.  But, a jerky takeoff doesn't sound particularly normal.  If it was something that happened with regularity, I think that it would be well-represented in the popular media, and the 747 would be a terribly unpopular aircraft.  Just my humble thoughts on the matter.

Good luck on finding out,
~Darrin

[Triple_7]

2 flights on Malaysia 747-400s.  Both full loaded passengers, fuel, for the trans Pacific flights LAX-TPE-LAX.  The takeoff from LAX was very long but smooth as far as acceleration, engines spooled up then right as the brakes released, full throttle using almost the entire runway to get up.  Takeoff from Tao Yuan on the other hand did experience a little bit of what you described.  Seemed like after the brakes released and we began picking up speed at full power, just starting to get pressed into the seat then suddenly the pressure was gone for a second feeling like the throttle was brought back some, then hard into the seat again till the end of the runway where we finally lifted off.  I was sitting right behind the wing both times, neither takeoff do I remember hearing the engines spool down at all.

Felt this on smaller regional jets a lot though, seems like full power, let off a couple seconds, then back to full power and up we go the whole time engines screaming at full thrust.

If I had to take a guess I would say wake turbulence could be the cause.  All times in the regional jets has been at a busy airport right after a larger jet took off before us.  TPE we were behind another 747 and didn't wait hardly at all before we followed.  LAX we only had a MD-80 ahead of us and I watched it get airborne before we even pulled onto the runway.

[Mictheslik]

2 flights on Malaysia 747-400s.  Both full loaded passengers, fuel, for the trans Pacific flights LAX-TPE-LAX.  The takeoff from LAX was very long but smooth as far as acceleration, engines spooled up then right as the brakes released, full throttle using almost the entire runway to get up.  Takeoff from Tao Yuan on the other hand did experience a little bit of what you described.  Seemed like after the brakes released and we began picking up speed at full power, just starting to get pressed into the seat then suddenly the pressure was gone for a second feeling like the throttle was brought back some, then hard into the seat again till the end of the runway where we finally lifted off.  I was sitting right behind the wing both times, neither takeoff do I remember hearing the engines spool down at all.

Felt this on smaller regional jets a lot though, seems like full power, let off a couple seconds, then back to full power and up we go the whole time engines screaming at full thrust.

If I had to take a guess I would say wake turbulence could be the cause.  All times in the regional jets has been at a busy airport right after a larger jet took off before us.  TPE we were behind another 747 and didn't wait hardly at all before we followed.  LAX we only had a MD-80 ahead of us and I watched it get airborne before we even pulled onto the runway.

Maybe the pilot went to 50% rather than 40% before going up to full and had to correct...

.mic

[MWISimmer]

I've flown 747s from LHR-SIN-PER and back twice, 6 legs in total (2 legs SIN-PER & back were in SIA 767s). I've never had that experience, always been smooth as you like.. Qantas, BA and Singapore Airlines..all the same.
BMI A320s..they're scary on rotation, very shaky.  :o

[Nexus]

I've flown 744's over the Atlantic several times, and never experienced the jerk.

The pilots will let the engines spool up (according to company ops), then press the THR button which engages the autohrottle and the thrust levers will move to takeoff power by themselves. And you wouldnt feel the "jerk " unless brakes were applied or thrust decrease by many percents.

The sensation of acceleration usually plays tricks on pax.
In simulator sessions the module begins to tilt slightly UP (yes upwards) during the first seconds of the take off roll.
As the "aircraft" picks up speed the module is progressivelly tilted downwards again.

Triple_7, could you elaborate on the wake turbulence theory?
I'm not really understanding what you want to say.

[Chris_F]

I need people who have flown on a 747 to answer this.


I have heard that as a 747 takes off the passengers fell jerks as if the plane is revving up by levels. An example is a car going 20MPH and then accelerates to 40MPH and back to 20MPH. I don't know if this is true. I don't think people inside would feel jerks but I have never been on a 747 so how should I know.

Only one flight on a 747 and I did not experience this.  The flight was exactly as one would expect an airplane flight to feel.  Only on a plane that was REALLY BIG.  :)

[C]

My only experiences of a 747 were from Heathrow to Singapore and back. On leaving Heathrow I remember thinking that the aeroplane felt like it was working hard; on leaving Singapore the experience left me knowing that it was working even harder! I thought we'd never leave the ground!

[Islander-O-NY]

keep in mind wing flex. with a wider wingspan comes more of it (and the engines are placed ON the wings). My thoughts are the wings bend slightly forward during accelerating, then pulls the plane foreward in a slingshot fashon. If I am right, this could happen as long as you have a large wingspan, weight and accelerating rate.

P.S. JFK sure has a nasty crosswind! (everyone, lean to the right!)

[Nexus]

If I am right, this could happen as long as you have a large wingspan, weight and accelerating rate.

Let's say you are.
If an airliner which has these wings flexing foward and backward, imagine it hits severe turbulence. The wings (not only flexes up and down like they should) start flex backward and forward.

Now, ask yourself what is going to happen as the wings begin to flex back and forth.
And according to your theory the flex must be significant.

Your thoughts about Yaw-roll tendencies?

[Chris_F]

Your thoughts about Yaw-roll tendencies?

Not to mention changes in AOA.  I doubt a wing could flex fore-back without significant twist as well.

[mrjake2002]

Well I don't know about all this, I've never been on a 747, but I'm pretty sure you'd feel this -> http://forums.airshows.co.uk/cgi-bin/uk ... =1;t=36783