737-800 Application of TO power while still aligning on centerline

[vonbag]

737-800 '
Application of TO power while still aligning on centreline

1. Is this amongst the standard procedures in some airline?
Is this contemplated in the "Users' Manual" of the Boeing 737-800?

From my very little experience in a light piston engine Aircraft (A/C), the application of TO power while turning on the RWY would create additional problems in gaining and maintaining directional control (also due to the P factor) at the initial phase of the takeoff (TO) roll (acceleration from taxi speed).

In a Boeing 737-800 (or 738, if you wish), on which I was a passenger (seated at the window, on the right side of the cabin),
the application of TO power while still aligning on RWY centerline -- which let me stupefied -- during a clock wise turn from the hold position on taxiway,
not only seemed to cause a RTO, but it seemed to have made the A/C unserviceable for the flight (all of us had to disembark and wait... for another A/C with another crew).
We all heard a very loud thump, with associated vibration, on the low middle right hand side of the A/C, under where I was seated (~ above right main landing gear - RLG).
This happened in concomitance of the application of TO power while we were still turning.
A few seconds after the power was cut, and TO aborted.
RWY elevation is about 30', wind appeared to be calm, OAT about 32 C, I cannot quantify humidity.
These are the facts.

I have searched in ANSV, the Italian Aviation Safety Board, but couldn't find any reference about this incident.

I also have exchanged messages with a very friendly and knowledgeable PPruner, I take the chance to thank him again.

2. What was the cause of the loud thump, the consequent RTO, and the A/C becoming unserviceable (at least for that flight, for what I know),
and is this in connection with (or, caused by) the "abnormal" (?) operation in the initial phase of the TO roll?

Amongst the possibilities, these two were told me:

"tyre burst"
"engine surge"

I had thought of a "wheel bearing" (on RLG)?

3. Note to the Moderator(s): if this subject/title is not appropriate for this Forum, please feel free to "move" or to "delete".

Thank you in advance.
Best,
Paolo

[porch monkey]

I would guess the 2 things are not related. Obviously, a failure of some kind has occurred, hence the abort. (I would say unrelated) The application of T/O power, (How do you know T/O power was actually applied, as distinct from setting approx 40 to 45 % and checking stable as is common practice?) during alignment wouldn't "cause" any particular failure.

[The Real Slim Shady]

Turning on to the centreline with idle thrust, GS less than 10 kts, and applying 40% -45% part way round the turn to stabilise the engines, doesn't make any difference.

Common practice if asked to expedite.

[vonbag]

Thanks for your replies!

...
(How do you know T/O power was actually applied, as distinct from setting approx 40 to 45 % and checking stable as is common practice?)
...

In fact, in the sequence of events before the occurrence of the anomalous noise and vibration on the right side of the A/C,
the only way I could understand that T/O power had been applied right there in the bend,
is from the very sharply pitching up noise of the turbofans (you know that noise very well, all of a sudden they seem to "scream", and as a PAX seated almost right next the source of it, it's maybe even sharper) and the consequent acceleration,
which anyone can feel with their senses, and always gives me a thrill.
This time the initial acceleration had a noticeable transversal component; sorry to comment this with my simple words:
I felt my back side pushed backwords and sideways on the left... me, like probably all the other PAX who were looking foward to enjoy of the T/O sequence.
I have heard many other times (as a PAX in the cabin) the engines just spooling up to a certain percent of N1 (depending on weight) for to start taxi or for verification of symmetrical thrust (and everything on green) at "taxi into position and hold" point, with or without parking brake set (I guess it is what you kindly wrote, about 40-45% N1).

I believe the take off sequence was rejected much before reaching V1, and possibly not even 80 knots, though.

Another imprecision in my initial post: the Airport elevation is just 7' (not 30'),
but this should be totally irrelevant.

Best regards,
Paolo

[captjns]

Nothing wrong about a gradual increase in thrust while lining up with the runway as long as takeoff thrust is set by 60kts, which accounts for ambient temperature and pressures.

If field lenght is not a question, I prefer the gentle push, the increase in thrust, rapid acceleration are not as sever on the passengers. In the long run its better for the motors too.

[ford cortina]

Vonbag, you admit you were not in the jumpseat of the flightdeck, but ignore what has been said!!!!

I am a Boeing 737-800 pilot, I also fly the 300, 400 and 700 version.

If you enter the runway, intending to expedite matters, you can stabilise the engines at 40% N1 as you turn on to the runway, then by hitting TOGA, that is the switch on the thrust lever to initiate the Take Off (or GO Around), the Thrust Levers will start to move to the selected takeoff thrust, of course the Autothrottle has to be on.

This takes a second or two, and the spooling from 40% N1 to approx 80 to 90% N1, takes a few seconds more. In this time it is quite possible to line the aircraft up nice and central. It sometimes can be refered to 'taking her on the roll'.

But then I am a mere airline pilot and not as knowledgable about such matters as the passengers, any time you wish to land the aircraft, be sure to let me know, I will of course let you know where you are going wrong with Themodynamics of fluid machinery.:eek:

FC

[vonbag]

Thank you kindly for your replies:

Porch monkey, The Real Slim Shady, Captjns, and Ford Cortina (I drove a Ford Taunus, the European Continental equivalent, as my first automobile!).

Vonbag, you admit you were not in the jumpseat of the flightdeck, but ignore what has been said!!!!

I am a Boeing 737-800 pilot, I also fly the 300, 400 and 700 version.

If you enter the runway, intending to expedite matters, you can stabilise the engines at 40% N1 as you turn on to the runway, then by hitting TOGA, that is the switch on the thrust lever to initiate the Take Off (or GO Around), the Thrust Levers will start to move to the selected takeoff thrust, of course the Autothrottle has to be on.

This takes a second or two, and the spooling from 40% N1 to approx 80 to 90% N1, takes a few seconds more. In this time it is quite possible to line the aircraft up nice and central. It sometimes can be refered to 'taking her on the roll'.

But then I am a mere airline pilot and not as knowledgable about such matters as the passengers, any time you wish to land the aircraft, be sure to let me know, I will of course let you know where you are going wrong with Themodynamics of fluid machinery.

FC


Dear Ford Cortina,
I have read and understood the answers to my points 1., and 2.

In my previous message, I just wanted to add more specifically what my perception had been in order to explain the title of my thread, which includes "T/O power", also in answer to the highlighted question of Porch monkey.

However, at the end of my previous message I had written:

Another imprecision in my initial post:...

with this I implicitly admitted that there were other imprecisions in my message.
Sorry for not having been clearer!!!!!!

Now, thanks to yours and your kind colleagues' answers,
I have a picture of what a "take her on the roll" is and serves for,
and will be prepared for it in my future flights (when I must remain in the cabin! :}).


Best regards,
Paolo

[vonbag]

Thank you, Moderators for the observation of my point 3.

A couple of messages were deleted, amongst which one of mine, slightly intense, it contained a compliment which shall never again be repeated.


I hereby consider the present case closed (like I had already mentioned, in the post that was deleted)

--, Paolo