BAe146 engine noise after take off

[RedEye4]

Don't shoot me for asking this question . . . but what the hell is that noice one hears from the 146 power plants a few minutes after take off, it sounds like engines 3 and 4 are just spinning up. Any takers . . .

[JimmyTAP]

That'll be the flaps retracting I would have thought.

JT

[Seloco]

I agree with JimmyTap - almost certainly the flap actuators, which are presumably mounted in the wing centre section and therefore effectively in the cabin roof. The noise sounds like screw jacks, and effectively seems to get louder as the accompanying aerodynamic noise lessens as the flaps go in. For landing the reverse is true, with both aerodynamic noise increasing and a rather pronounced pitch change as well.

That's one thing you can say about being a pax in a 146/RJ - you can at least see everything happening!

[RedEye4]

Thanks folks for those responses . . . you've answered something which has been bugging me for ages . . . beautiful a/c - one of my favs.

[PAXboy]

I alsways find it useful when I hear the flaps running out - then I know it's time to stop reading the book as we are approaching the funny hard stuff that we have to sit on. So then we can get the go-juice and go somewhere else!

I have liked the 146 (purely as pax) from my first ride in it, which would have been late 1987, when it was introduced on the LHR ~ IOM run.

Great machine, looks good on the ground and in the air. Get's up and goes and does neatly. I have heard all the gripes about it but then but this machine gave birth to many RJ ops, I am sure.

[Speedbird48]

It is not the engines or the flap actuators. The noise is aerodynamic and comes from the airflow through the inner flap fuselage gap as the flaps are retracted, or extended.
Sounds a lot like a kamakazi to those not in the know and a lot of operators add a comment in their pax briefing so as not to scare the little old ladies in the back.
There was an attempt to cure it on the Avro RJ version but it is still there, although. not quite as loud.

[Final 3 Greens]

Speedbird 48

Spot on. The cause of the odd white knuckle for poor nervous pax not in the know.

I've never heard it announced over here, but I have interevened a couple of times over the years to say 'don't worry, it's normal - I have a pilots licence adn I know.' I don't tell them it's only a PPL to drive PA28s, as I reckon that would ruin the cathartic effect and subsequent sighs of relief :-) However, under the circumstances I reckon this sleight of hand is justified.

[safetypee]

Not quite spot on Speedbird and Finals…

The flap howl originates from the flap wing gap (slot) along most of the wingspan. The source is aerodynamic. Most high lift wing / flap combinations have such a noise, often heard from the ground. You can just hear a similar noise in the cabin on Airbus A320 when sitting near the wing leading edge (Kruger flap?). The difference between the 146 and Airbus is that the A320 has a low wing at cabin floor level that masks the flap noise, but the 146/RJ has a high wing position above the cabin. The 146/RJ also has more lift – still the highest CLMAX for any civil aircraft.
The noise is very speed dependant, hardly noticeable if the flaps are retracted at Vfto or lowered at min maneuvering speed, but you will get max howl when selecting flaps at flap limit speed.
BAe did test fly a partial fix, a wedge shaped spoiler on the underside of the wing; not too successful I guess, as it was not put into service.
Another other noise with flaps down was a mild drumming in the rear cabin; this was fixed by use of flap track shutters over the inboard flap track (fuselage gap; RJs only?). If you get a drumming noise at approx 180 kts, 18 flap then get the shutters regreased.

[False Capture]

Safetypee,
Good info, as you say BAe spent thousands of pounds tying to cure the howl, this wasn't just on the RJ but on the original 146 as well. The RJ (not BAe 146)series were fitted with flap track covers which help to reduce some noise. These sometimes get stuck in the down position when the flaps are retracted at the end of the flight, this often leaves inexperienced FOs scratching their heads during walk-rounds. Whilst this does not present the pilots with a problem/issue the noise in the cabin is increased. The cure for this is a spot of grease - the same solution as an airbrake which keeps deploying itself on the ground when the hydraulics are selected off. :ok:

[Capt Claret]

Unless I very much have the wrong end of the bull, several of the 146s I fly have flap track 'shutters' fitted.

I'm pretty sure they are fitted to all marques (100/200/300) in our fleet.

[fruitloop]

safetypee
I hope that you use the right grease and only put it on the bearing and not all over the track !!

Capt Claret.
I could be wrong but I thought that they were only fitted to 200/300 (and not all as per a/c effectivity)(some mil spec units are also optioned but data is hard to obtain)

Another noise area is pylon track boat vib's (ribs 6,10 mainly)with any flap selection.

Arrh!! the moanful groan of two hydraulic systems (through planetary gears)trying to move universal equiped driveshafts to gearboxes which drives chains(read Malvern Star)to an intermeadiate drive (primary or secondry)screwjack (again watch what grease you use as it has a habit of freezing up giving erroneous flap fault warnings) brings a chuckle to mind.
Have a nice day !!

[Capt Claret]

Took a look at a 100 (Delta) as I walked past it on the apron today.

It was fitted with 'shutters'.

[fruitloop]

Capt Claret
I stand (semi)corrected as to the fitment of shutters on 100 series Delta.(E1***)may have had mod 00790C carried out by a prior owner.FYI it was also not carried out to a lot of 200 series a/c as well when they left the "factory"
Cheers