Bae 146 / Avro RJ banshee flap extension noise
 

Hi all,

Have flown on several 146s / Avro RJs of different ages and all seem to have this weird banshee sound as the flaps extend to the first stage. Is this caused by the disruption of the airflow over the wing or is it the actual noise of the mechanism working away that you might not be able to hear on low-wing aircraft?

Cheers.

I remember one of the two original 146's that went to Ansett, during build we couldn't get rid of the 'flap judder'. We changed the flap screw jacks, carriages, flap tracks and even the flaps themselves and it only marginally improved the situation.

Don't know if they managed to solve the problems with the RJ's before they got the chop.

i just noticed it too this afternoon on route back from Edinburgh to City Airport - rare I fly on 146's so wondered about it at the time - didn't sound like the happiest mechanism in the world!

Gents, whilst the comments about the noise being created by the mechanism being the culprit for the noise is quite plausable. I would suggest that the noise is airflow disruption. The 146 if I remember correctly was designed with a high lift wing section in order to allow it to operate on short strips and have good climb ability linked with its four engines.
Failing that argument / reason - you can hear the 'banshee' noise from the ground, therefore highly unlikely to be mechanical noise. Also the noise continues after the flaps have stopped travelling.
All that said, first time I travelled on one and the flaps where selected the noise certainly startled me and practicaly gave the lady sat next to me a panic attack. Maybe a passenger warning is in order for any new / nervous passengers.

The noise is infact disrupted airflow so your guesses are correct. Rather than being over the wing it is between the root of the wing and the fuselage. As flap 18 (1st stage) is lowered the air is forced between the gap between the flap inside edge and the fuselage which creates what you are hearing. It seems to be most prevelent between flap angles of 10deg to 18deg when travelling in either direction. This would explain also why a certain amount of noise remains after the initial extension. The running of the flaps themselves is actually very quiet (from experience of extending them whilst on the ground).

But then have any of you heard it whilst you're on the ground and it's happening above you - sounds like the old girl is just about to fall out of the sky!

As mentioned the noise is airflow related not mechanical. If the noise wasn't there, us 146 pilots wouldn't know thet the flaps were travelling! :p

In the co I work for mention of the noise is indeed made towards the end of each safety demo, to the affect that, "shortly after take off and prior to landing you will hear an airflow induced noise associated with the extension and retraction of the wing flaps. This noise is normal." :uhoh:

I'd be really interested to know if the 146 was to be newly certified in 2004, would certification be granted, given said noise, and not withstanding some of the other design characteristics of the 146.

Capt Claret; If you pilots would extended the flaps at the correct speed the aerodynamic noise would be much reduced. Flaps up at Vfto, flaps out at min manoeuvre speed.

Certification does not consider this type of noise.

BAe did fly prototype modifications to reduce the noise, but the wedge shaped fairings under the wing weighed 60 kg - nearly 1 pax in payload.

Ever blown across the top of a beer bottle?

I understand that much work was performed to fix this issue, but that a repeatable solution was not forthcoming.

1st time I heard it, I thought the engines were about to fall apart. I now actually look forward to it and take rather twisted pleasure in watching the reaction of others who've not heard it before.

Didn't the BAC 1-11 have a similar flap extension noise ??

Aaaaah, the 1-11, what an aircraft... No idea about airflow noises though!

Thanks for all the replies, very interesting to hear. Was on an RJ between MAD and MAN the other month and a Spanish family nearly jumped ship when they heard the flaps extending. I chuckled away in an "I'm a seasoned flyer and it doesn't scare me" type way as hinted by Noise Unit!

Ta ta.

Every time I have been on Qlink 146 they have given a warning about the noise, so obviously enough people shat themselves and then complained to warrant the warning.

safetypee

On take off - Flaps retracted at Vfto, no faster than Ver until flap zero.

On approach - Flap 18 selected at Vfto +15 (company minimum). Vfto +15 is often signifficantly below the max speed for extension of Flap 18, which is 200kt, 205kt, 210kt or 215 kt, depending on which airframe one is flying. :\

What part of this procedure is the incorrect speed?

Flaps still howl.

While on the subject of flaps. How can one type have so many different flap extension speeds for a given flap setting?

Different flap speeds, different MLW's, different Pax oxy systems, differences in memory items, different FD layouts, etc etc etc.
Doesn't make the day any easier.

Flap Howl
 

I work as c/c on the 146 and we do not mention the 'flap howl' to the pax at all. We never get anyone asking what it is either!

It is louder on the older style -200's, though they managed to calm it down a bit on the later-build -200's and 300's and is probably the same system incorporated on the RJ's. I believe they fitted shutter-like slats over the flap track which helped to reduce some of the noise.

The howl is useful to us c/c though because it gives us a rough indication of how far into the t/o /decent we are, it's also kind of a re-assuring noise when you are used to hearing it day in, day out!

Personally I think the noise is quite a nice touch! Personalises the aircraft a bit and what's more you feel like you're actually flying! I mean, can you imagine a PA28 with minimal noise? How boring would they be!

PS - Was surprised to go all the way from Manc to Madrid in 146. Also done EXT - AGP and it seemed to make it there with all 4 engines still running. I imagine it's the furthest end of the range though is it? Full loads on both flights and return as well. Impressed!

Edited for appalling grammar. My Mum would be horrified.

The only sound I have been able to liken it to is that of a Tube train entering a station.

With reasonable experience of SN Brussels RJs vs. 146s, it is certainly more pronounced on the elder models.

But love the takeoff performance....that noise abatement departure out of Zavantem takes some beating!

Just as a point of interest (to some)the flap shutters (mechanical on inboard flap tracks)are disconnected at approx 14 degrees of flap movement (12 degrees indicated in cockpit)

DVR6K

I don't know the distance of the routes you mentioned but regularly fly Alice Spring to Perth, 1069 nm plus STAR. Substantial icing conditions and or more than 30 holding and or HWC >100 kts will see a tech stop, but its more common to make the trip in one hop.

From memory 4hrs 6 mins (in ~100 to 120 kt headwind but clear conditions) is the longest block time I've had.

Please see an extract from my post to a similar thread on this subject some time ago – use search ‘flap noise’.
The BAe146/Avro RJ 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. The primary 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 manoeuvring speed, but you will get max howl when selecting flaps at flap limit speed.

Another other noise with flaps down is a mild drumming in the rear cabin; this was fixed by use of flap track shutters over the inboard flap track. If you get a drumming noise at approx 180 kts, 18 flap then get the shutters regreased. The howl and to a lesser extent depends on whether the aircraft has pannier tanks fitted or not.

I hope that the above helps with Capt Claret’s question on the intensity of the noise, but don’t forget that turning / increased ‘g’ will increase the noise, and that every aircraft has its own characteristics due to rigging, sealing strips, repairs, etc. There will always be some howl.

The different flap extension speeds are predominantly governed by aircraft variant (Max wt), but particularly by max zero fuel wt. Note that for the very heavy wt 146-300 / RJ100 aircraft the Min Man - Vfe gap closes quickly.

safetypee

My hearing must be better than I thought it was, or your's is worse than you realise.

Whilst I agree that the howl is louder the faster the airspeed when the flaps travel between 0 and 18 degrees or vice versa, even at Vfto the noise is still very noticeable.

Click here to save from searching for safetypee's aforementioned thread.

Re: Why does the max zero fuel weight have a bearing on the maximum speed for extension of flap 18? With regards to Max Wt, I understand that a heavier 300 as compared to a 100 or 200 will need a higher Vfto, but I don't understand how this affects the maximum speed for Flap 18?