Scary takeoff
 

I was on AA158 yesterday and I experienced one of the more nerve wracking takeoffs I've ever experienced in over several hundred flights.

Immediately after takeoff the plane started to turn to the left, no big deal. However after maybe a only a few thousand feet in the air, the plane's engines noticeably got quieter and we started to lose altitude. It struck me as particularly odd because the engines sounded like they had been cut and I know that turning requires more engine power, so I figured that's why we were losing altitude. This continued for a few seconds and then we very slowly started regain altitude but for a good minute or so the plane wobbled dramatically to the left and to the right and it felt like it was struggling to gain altitude. Eventually we leveled off and reached cruising altitude.

My girlfriend (also a frequent flyer) and I both were commenting how that take off seemed uncommon and were pontificating with our laymen knowledge about what might have been different.

I acknowledge I'm nothing more than a PAX who lurks this forum and other pilot/flying forums, so my knowledge is extremely limited. I am curious as to what might have happened? Was my nervousness legit?

It sounds like a perfectly normal noise abatement procedure.

Noise abatement Departure Climb Guidance

Hi zethon and welcome to the Cabin of the PPRuNe machine. :ok:

DaveReidUK has given the most likely reason for the change in noise and aircraft attitude. The procedures following departure vary according to each airport and aircraft type so the departure point is important.

I know myself that, when the engines are throttled back for noise abatement, it can sound as if they have almost been shut down - because the sound level you have just been hearing for a minute or two is so much louder. However, these procedures are used every day.

I hope that you stay here and enjoy other aspects of being a 'PAX' and contributing too.

In addition to the above two comments, reduction of power together with either leveling off or simply reducing the angle of attack will very likely give you the feeling that you're sinking. But you're not.

A long time ago in BCAL days we often used the easterly runway to start our trip to South America via Lisbon or Madrid. As we only had fuel for to the first stop so we were very light. The stop ht at LGW was 2000ft and if the auto throttles were engaged ihe aircraft reached 2000 ft in a few seconds and then the thottles woud close. Very scary for the pax as we became a glider for a short while. We soon learnt to use some manual skills to make for a more relaxing departure.

The PDF link that DaveReidUK gives is very good. Not just because it explains the timing of thrust reduction but neatly covers the transition between 'intial climb' and 'climb to altitude' phases of the flight. Retracting the flaps whilst the engines are pulled back a little, helps reduce the noise of that action - as heard on the ground.

One other thing about the noise abatement action depends on where on the aircraft you are sitting. Because the aircraft nose is lowered, for flap retraction, if you are forward of the point of rotation your seat will go down! Not far but it does. In the same way that if, for example, you are sitting near the back of an A340-600, when the nose lifts - you will go down before you go up!

It's worth remembering that he human body can not feel speed, what you sense is acceleration.

In other words, when the engine thrust reduction takes place (which is standard in any departure for noise abatement as well as reducing engine wear) then you will feel an acceleration downwards. This will feel like a sinking sensation and has scared more than one person.

My first time in the flight deck in proper IMC I had a few interesting sensations when my body tried to tell me the aircraft was going weird things. However I could easily look at the instruments and see that was not the case. But my body was doing a very good job of trying to convince me we were in fact turning when we were not, or that we were descending when we were not. Very strange at first but once you're aware of it you can adapt to it.

Flight Track Log ? AAL158 ? 15-Mar-2017 ? KMIA - CUN / MMUN ? FlightAware

The aircraft leveled out at 3000ft (probably due to traffic) then continued the climb after about one minute. At no stage did it descend. It commenced the left turn on reaching 3000ft.

Edit;

Looking at flightradar24, the conflicting traffic was probably N216PK, a PAC P-750 climbing through 4000ft south to north.

Yu didn't lose altitude. All that happened was that the engines were rolled back slightly as no longer requiring full takeoff thrust and you leveled out momentarily and then started ascending again. Quite typical takeoff really, especially when noise abatement procedures are in place.

But it can certainly FEEL like the engines have died and you are falling.

Absolutely nothing to do with noise abatement. I don't know of any noise abatement procedures that cause you to fly level at 3000ft for over a minute (please correct me if I'm wrong).

In this case N216PK was climbing across the path of AA158. ATC realised that there was a conflict and instructed AA158 to level at 3000ft. If this was done at short notice then there would be a rapid reduction of power. AA158 passed just behind N216PK, 1000ft below. That's how ATC earn their money.

Assuming Airclues data is correct the sound would have been considerably different to a normal, unrestricted climb. I'm also going to guess that the first change may well have happened 1,500' before level off when a lower rate of climb was selected (to prevent a TCAS warning). The level period may well have been flown slowly due to a local speed constraint.

Flown many times and had a few "interesting" takeoffs & andings...one of the best was KLM out of IAH in October 2008

Nice takeoff, smooth as silk only to be interupted by the pilot to the effect that we should not be alarmed by the turn to the left that was about to be made

No worries....there I am sat by the window, left side of the 747 Combi looking straight down the wing as we perform the most perfect pirouette and I'se looking right into the crown of a rather large and fairly close palm tree that has appeared below the winglet...

Yup....nothing to worry about...as the stranger in the seat next to me suddenly grips my arm like a vice, changes to a strangely pale colour, closes his eyes and monbles something along the lines of "oh shhhhhhh"

Standing one's fully loaded 747 on a wingtip to return to the airport in a hurry is a great way to start a flight to Amsterdam....especially when inspecting a palm tree from above