Gulf Air GF236 AbuDhabi-Muscat - jan 4 , 05

[Bu7abes50]

I would like to share an occurance purley as an aviation enthusiast who was quite alarmed when it happened.

Flight was GF236 abu-dhabi to muscat on Januray 4, 2005 (A320). A minute or so after being airborne the pilot suddenly and drastically reduced power and the aircraft felt as if it was descending ,2 seconds later he applied full power and then again right away reduced power and finnaly reverted back to full power.

He also seemed to make a full turn as if going back to the airport. Here is where it gets very interesting. On landing at Muscat and while walking down the staircase I heard a lowed and unusual noise coming out of the right hand engine. The noise sounded like some metal peice was stuck between the fan blades and making a crunching effect as the blades continued to turn during engine shutdown.

One of the ground staff had a torch light and was curiously examinig the front and back side of the engine casing.

For those who can shed a light on this flight, Iam very curious to know what went on. I fly alot on the A320 and I have never went through a flight like this where the captain just about a minute after takeoff significantly reduces power then back up then again back down then up... seemed as if for a moment the engines were out of control...

Thanks

[Notso Fantastic]

Everything you describe is part of normal aviation. When you felt as if you were descending, the aeroplane was levelling off rapidly- maybe the air traffic controller told them suddenly to do it, then cleared them to climb again. Quite normal.
The sound you heard when getting off is the wind blowing through the engine and rotating it. When it rotates at low speed, the fan blades bang into each other and it sounds as if a metal stick is being run along a metal fence. You should hear 4 engines on a Boeing 747 all doing it together! Nothing was out of control except your nerves!

[hobie]

Nothing was out of control except your nerves

Your a "hard Man" Notso! :p :p :p

:ok:

[Skeleton]

This reminds me of.....

The time I was in a VC10 at max AUW climbing out of BZN at full chat, when 4 RR conways went deadly quiet and we levelled (at 3,000ft I later learnt) rapidly. I remember the deadly hush and quizical looks around the cabin :confused:

30 secs later power up and we were on our way to have the same thing happen not less than a minute later...

What was it? Normal aviation - a busy airway we could not get into or across and a stop climb from Brize radar whilst they tried to get someone from London to accept us!!

Sets the nerve ends a jangling though I grant you.

[Notso Fantastic]

The 10 is a wonderful noisy beast. I seem to remember our noise abatement procedure was full chat for 90 seconds, throttle back to lower power and lower nose (causing great alarm) for 90 seconds(?) further, then normal climb power- then presumably they levelled off.

I think we've spoilt you lot with gentle handling, so the odd time when things get a little more lively you all think you're doomed! What it is is pilots handling the aeroplane in a perfectly acceptable way- they have no idea you are sitting there, knuckles white, feeling you are about to levitate.

[vfenext]

The auto thrust on the 320 can give pax a start every now and again. If you have an early level off the power sounds like the engines have failed. Follow that with a climb, and the power goes from idle to full climb in a short period of time. Sounds scary sometimes but it's normal!

[Bu7abes50]

Your a "hard Man" Notso!

hobie...hmmm seems you have a fondness for "Hard" men :p :p :p :p your one lucky man Notso! and thanx for the feedback :D :D

[jettesen]

The same happpened to me. I was on the A330 muscat to LHR on the 4th jan. Sudden loss of power just after take off, then sudden climb about 5 mins later.

[HEATHROW DIRECTOR]

Jettesen... As has been mentioned earlier, that's quite normal. To level off at a particular altitude on climbout the engine power is reduced. Equally, on descent the engine power is reduced until the a/c approaches its cleared level and then the power is increased. In a busy environment such happenings will be quite common. Eg climbing out of Heathrow it's common to be stopped at 6000 ft... then a few minutes later receive climb to a slightly higher level... then a few mins later a highe level... etc, etc. Watching the dear old Conc on noise abatement used to be fun - it would rocket upwards with full re-heat, then the torch would go out and the thing would appear to drop like a brick! In fact it was just the noticeable change in rate of climb.

[Bu7abes50]

Gentlemen what you are all talking about is fine and I understand the mechanics of leveling off until receiving clearance to climb again and happens on most of the flights ive been on.

However as i've mentioned in my first post, what happened on GF236 wasn't just a normal leveling off then climb, it was a sudden throttle back followed by full thrust just 10 seconds later , and again a throttle back 5 seconds later and finnaly full thrust in also about 5 seconds later.

So it was a multitude of throttle ups and downs simultaneously after each other which had raised some eye brows from several of the passengers...

[vfenext]

It's all been covered at this stage. No problem was reported with this flight. A case of a little knowledge........me thinks!!

[TEC TEC]

How do you know it was the captain reducing the power?

When a medium/ heavy jet aircraft is leveled off at low altitudes it is sometimes required to idle the engines, especially when light like on a short hop from MCT to AUH ......

Keep cool :E

[Seloco]

A good suggested therapy here is to book a B757 flight out of the wonderfully named John Wayne International airport in Orange County, CA. Vicious noise abatement procedures require a max energy take off - rather fun in itself - followed by complete throttle back at the airport boundary, to be held until you reach the sea, at which point the climb is recommenced at full wellie. Each time I have done it the PF has patiently explained the procedure to the pax during taxi, thus preparing one for the various stomach churning events to follow.

Incidentally the clattering noise one hears when an engine fan is turning in the wind is not the blades hitting each other, but rather the noise of each blade moving in its "fir tree" mount as it alternates up and down during rotation. Once the fan is powered up the blades are firmly held out due to their centripetal acceleration.

[Astra driver]

Right on seloco!

I can attest that the departure from SNA and many other airports such as Oakland which require a level off shortly after takeoff as well as a 200 knot speed restriction due to being under Class B airspace (although I know a lot of guys that ignore this restriction) can require some aggresive throttle movements form the pilot. It can be especially fun when the aircraft is light and wants to go up like a homesick angel, trying to accomplish the level off with a speed restriction smoothly can be challenging.

[lomapaseo]

Incidentally the clattering noise one hears when an engine fan is turning in the wind is not the blades hitting each other, but rather the noise of each blade moving in its "fir tree" mount as it alternates up and down during rotation. Once the fan is powered up the blades are firmly held out due to their centripetal acceleration.



More accurately describing condition is that blades do rock in their attacments be they fir-tree types or dovetail types When they rock at windmill speeds they may lean over and close down some clearance that would never be there at high centrifugal stress. If the blades are the type with clappers,snubbers or shrouds on their airfoil, thats where the noise comes from. If the blades are of tne shroudless variety then indeed their platforms at their attachments may hit.

Experience has shown that the loudest noises come from the shrouded blades falling over at TDC and hitting a neighbor at each revolution of the fan <90 RPM

[Kilo-club SNA]

Flew out of John Wayne for a few years and lived just south of the runway (to close to benefit from the noise abatememt porcedure..)

On one occasion (without me onboard) the captein brefied the pax
"Ok, for those of you who havn't flown out of John Wayne before we have a special procedure to make sure not to bother the people who built their houses close to the airport and are now complaining about it...." Pretty funny but I imagine there were a few on board who were active complainers...:cool:

[ironbutt57]

Yup..the old "Santa-Ana cut-back" what a disaster waiting to happen that one.....gonna be a lot noisier when an engine packs it in during that procedure, and someone rolls over on their back and stoves into the community....:confused: in addendum to the comment relating to the GF power decrease...both airports have initial low level-off altitudes..3000', so in an aircraft that is relatively lightly loaded, it reaches this altitude very quickly...most often we are cleared to a higher level before "altitude capturing" at 3000', but not always, and the power comes back quite rapidly to avoid overshooting airspeed limits...hope this sheds some light on the subject...disconcerting for pax..yes, can be...under control....absolutely!!:cool: