Posts about: "Noise Abatement" [Posts: 17 Pages: 1]

10,000kg in a trim tank? No, I am really not that stupid to think it was all used for trim but I am beginning to realise just how little I knew about this technological wonder of the skies. Also wish someone had recorded her being rolled (like the B707 when being displayed). Now that would be something that would stand along side the noise abatement takeoff or maybe not. The T/O is impressive!!

M2dude and ChristiaanJ, please keep posting any anecdotes that you remember about this incredible aeroplane. It really is fascinating learning about the technical side from those who actually knew her.

Always more nose up than a conventional a/c.

As you note, about 4 in the CRZ. About 10.5 degs on approach.

As part of the performance calcs we calculated a 'theta 2' value of pitch. This was bugged on the ADI with a little bug controlled from a thumbwheel on the yoke - at all speeds very accurate pitch control was required, hance this device and the ADI being calibrated in 1 degree increments.

Theta 2 was attitude reqd to obtain V2 in the first segment with one engine out, i.e. the target attitude if an engine failed after V1. Once the gear was up (second segment) one would pitch up a little to hold V2 until 600ft then start initial accel.

On all engines, one held it until 250kts then pitched up to maintain that speed. You'd typically reach it before passing over the M25 departing LHR to the West.

In all cases, as soon as SID altitude or noise abatement limits had been reached you went to the barber's pole asap (400kts initially) as this was where best performance lay.

Galaxy flyer -

TO perf calcs were basically sinilar to a susonic type, which involved a tabulation for each runway in a manual and an A4 proforma.

It was no more complex than a 'Classic' 747, but with a slightly different emphasis - e.g. all take-offs at full, reheated thrust, calculation of fuel transfer or burn off during taxy to achieve TOCG, calculation of timings and thrust setting for runway-specific noise abatement procedures, calculation of theta 2, and planned fuel flow and P7 to set in the take-off monitor (A system designed to aid, but not substitute, the decision of the FE as to whether TO thrust had been achieved, as well as auto selection of contingency power if a failure was detected).

You'd also determine whether a single reheat failure was acceptable that day - the little '3' or '4' bug at the lower left of the engine instruments was set as a visual reminder.

Not sure what you mean by Vzf? No flaps on this machine, so no change. May be a difference of nomenclature. Since there is no defined stalling speed for a delta (by conventional standards we lifted off about 60kts below 'stalling speed') Vzrc was substitued. This is the speed at which full thrust would result in a zero rate of climb. On three engines, this was the basis of the perf calculation, but we also calculated 2-eng Vzrc's gear up and gear down. IIRC they would come out at about 250kts/300kts.

On a transatlantic sector you would do all this and the speeds would invariably be within 5 kts of 160/190/220kts. (V1,Vr,V2)......

In the end we had a little handheld computer which would perform take off calcs, but to be honest it was only a minute more effort to carry out a manual calc.

ChristiaanJ

The way I remember it was

"3-2-1 now" was to ensure that all 3 crew members started their stop watch at the same time i e on the call of NOW as that was the point the throttles were moved rapidy to the forward stops. In fact the noise abatement timing assumed the engines were allowed to accelerate at their own rate, rather than at a rate controlled by the crew

"Green lights" served two purposes
1] To allow the pilots to have a quick reference as to the state of the engines during the Take off

2] Prior to the nose gear mod ona rough runway [when it could be difficult to red the engine instruements] it did give the F/E an indication that the engines had reached the basic power required

3/4 tab. as different T/Os required diferent minimum reheats either 3 or 4
The small 3/4 tab was there just to visually remind crew as a back up to the briefing whether they were on a 3 or 4 reheat day

I have not I believe been on an aircraft where you run up to full power before releasing the brakes, but there again the memory could be fading, and I am sure the sudden release of brakes at full power would not do them any
good

Mind you I could be wrong

They weren't used for take off because there was no relevant mode. The initial climb was to hold 250kts after takeoff until a predetermined time for noise abatement (a little over a minute ex-LHR, less ex-JFK) and then start to accelerate after the NA thrust reduction.

It was a balancing act and different for each departure - the RoC actually went up the faster you went so you were easing up, maximising the acceleration, while ensuring you (just) made the SID alt requirements.

So, apart from a few seconds holding 250kts, there really wasn't a mode that would work in pitch; you would have to take vert speed and be constantly asking the NHP to select different VS's and HDGs and they had quite enough to do already. No benefit, so don't use it.

Once you'd got to Vmo during the SID (it was 400kts at that point) you could use Max Climb mode (see earlier discussions) and that was generally when the FD was engaged.

It was permissable to engage the AP at an early stage, in which case HDG mode and Pitch Hold would be used, but it was more effort than hand-flying, less accurate and less fun so that was a rare event.

On approach, if an ILS was being flown, you are correct that the FD could be used, although for a typical approach it needed to be off at 300'. This was because wherever possible we flew a 'Reduced Noise Approach' (again, see earlier comments) which consisted of holding 190kts to 800' then reducing to final speed to be stable by 300'. AP/FD had to out by 300' in this case, owing to the very tight pitch control required for which it wasn't certificated (although it could carry out a very good coupled approach and landing if given a more stable approach).

In summary - a very 'hands-on' aeroplane. And all the better for it

Mr Vortex
First of all, 'welcome aboard'; I'll do my best to answer your queries.
The area of the primary nozzle Aj, was varied for 2 'primary' purposes :
a) To act as a military type 'reheat' or 'afterburning' nozzle; opening up to control the rise in jet pipe pressure P7, as reheat is in operated.
b) To match the INLET TOTAL TEMPERATURE RELATED (T1) speed of the LP compressor N1 to the HP compressor N2 against a series of schedules, ensuring easch spool is as close as safely possible to its respective surge boundary, (with a constant TET, see below) and therefore at peak efficiency.
Now, in doing this a complex set of variables were in place. As the nozzle is opened there is a REDUCED pressure and temperature drop across the LP turbine. This has the effect of enabling a HIGHER N1,as less work is being done by the turbine. Also the change (in this case a decrease) in the temperature drop across the turbine will obviously affect the turbine entry temperature, TET. A closing down of the nozzle would obviously have the opposite effect, with a DECREASE in N1 and an INCREASE in TET.
In practice at a given T1 there was always an ideal N1 versus N2 on the control schedule (known as the E Schedule), the TET staying more or less constant from TAKE-OFF to SUPERSONIC CRUISE!!
As far as noise abatement went; when reheat was cancelled and power reduced after take-off, an E Schedule known as E Flyover was automatically invoked. This had the effect of driving the primary nozzle nearly wide open, reducing both the velocity of the jet efflux and in essence the noise below the aircraft.
The real beauty of this primary nozzle system was that it really did not care if the engine was operating dry or with afterburning ('it' did not even know). P7 was controlled against a varying compressor outlet pressure, the variable being controlled by a needle valve operated by the electronic engine controller. (If this is unclear I can post a diagram here that shows this control in action).

As soon as I receive back the majority of my technical notes that I have out on long-term loan (I've requested their return) I will post a schematic here. But for now; The tanks were vented to atmosphere via tandem vent galleries, the two vents openings being on the left hand side of the tail-cone. At an absolute static pressure of 2.2 PSIA (around 44,000') twin electrically operated vent valves, also in the tail-cone, would automatically close; the tanks now being pressurised via a small NACA duct on the right side of the fin. A tank pressure of around 1.5 PSIG was maintained by the action of a small pneumatic valve at the rear of the aircraft. There was massive protection built in to guard against over-pressure (eg. if a tank over-filled in cruise).

I hope this answers some of your queries
Best Regards

Dude

Mr Vortex
More or less you are correct yes, but remember that schedule selection was more or less automatic. ( E Flyover was armed prior to take-off, and E-MID during approach by the E/O, otherwise it was more or less a 'hands off' afair).
Oooo no, we are way adrift here I'm afraid. I'm trying not to get too 'heavy' with this explanation, and I've enclosed below the Rolls-Royce E Shedule diagram to try and help clarify everything. (I've edited out the exact equation figures in deference to Rolls-Royce). Where N1/√θ and N2/√θ is quoted, the term ' θ ' related to T1 in degrees K/288 . (288 deg's K being 15 deg's C). The hotter things are the higher the spool speed scheduled is, and visa-versa for lower temperatures. Only at a T1 of 15 deg's. C (Standard day temperature) does N/√θ equate to N. (But remamber that T1 is TOTAL temperature, that varies with Mach Number).
The use of E LOW above 220KIAS was not only strictly inhibited by the automatics, if you over-rode the automatics and 'hard selected' E LOW , the aircraft would fall out of the sky when reheat was cancelled at Mach 1.7. This was because the low N1/√θ scheduled by E LOW would now invoke an N2/√θ limit (The E3 Limiter in the diagram) and claw off fuel flow by the tonne.
The most efficient schedule for supersonic cruise was E HI which again would be automatically selected.
E-MID was automatically selected during afterburning operation, to minimise the chance of an N1 overspeed on cancellation of reheat. E-MID could also be selected by the E/O for noise abatement approach.
E Flyover was as we discussed before used for take-off flyover noise abatement as well as subsonic cruise if desired. (If Mach 1 was exceeded with E Flyover still selected, a yellow NOZZLE light illuminated and E HI would be automatically selected.
I sincerely hope that this blurb is not clear as mud, feel free to ask away.
Nope, that is the beauty of it all. Because of the part choking of the LP turbine section of the engine, the pressure changes due to Aj variation were felt exclusively by N1 and not N2. (Clever, these Rolls-Royce guys ).
Regards

Dude

Nick Thomas

... Am I right in assuming that TLA stands for throttle lever angle? ...

Yes. TLA was a TLA for throttle lever angle.


... did setting the throttles to a certain angle then give a known thrust setting? ...

Yes, the calculated thrust required at the noise abatement point. The TLA was calculated by the NHP (as part of the take-off performance calculations) and later cross-checked by the Captain and F/E.

I don\x92t know whether it is audible on the DVD, but the checklist question was \x93Clock and TLA bugs\x94 .

If not already set, the Captain and F/O would set the noise abatement time on their respective (countdown) clocks and the F/E would cross-checked them, and, if not already set, the F/E would set the TLA bugs (on an engraved scale on either side of the throttle quadrant) to the noise abatement setting and the Captain and F/O would cross-check him.

The checklist response was \x94Set\x94 .


Best Regards

Bellerophon

JFK 31L, Kennedy 9 Departure, Canarsie transition, Concorde climb


Speedbird 2, cleared take-off 31L.

You call 3-2-1 Now , start your stopwatch, pre-set to countdown from 58 seconds, and slam the throttles fully forward till they hit the stops. Four RR Olympus engines start to spool up to full power and four reheats kick in, together producing 156,000 lbs of thrust, but at a total fuel flow of 27,000 US gallons per hour. A touch of left rudder initially to keep straight, as the #4 engine limiter is limiting the engine to 88% until 60 kts when it will release it to full power. The F/O calls Airspeed building, 100 kts, V 1 , and then, at 195 kts, Rotate . You smoothly rotate the aircraft, lift-off occurs at around 10\xb0 and 215 kts. You hear a call of V 2 but you keep rotating to 13.5\xb0 and then hold that attitude, letting the aircraft accelerate.

The F/O calls Positive Climb and you call for the Gear Up . On passing 20 feet radio height, and having checked the aircraft attitude, airspeed and rate of climb are all satisfactory, the F/O calls Turn and you slowly and smoothly roll on 25\xb0 left bank to commence the turn out over Jamaica bay. Some knowledgeable passengers will have requested window seats on the left side of the aircraft at check-in, and are now being rewarded with a very close look at the waters of Jamaica Bay going by very fast! As you accelerate through 240 kts, the F/O calls 240 and you pitch up to 19\xb0 to maintain 250 kts and keep the left turn going to pass East of CRI.

54 seconds from the start of the take off roll you hear the F/O counting down 3-2-1 Noise whereupon the F/E cancel the re-heats and simultaneously throttles back to noise abatement power, around 96% as you pitch the nose down to 12\xb0 to maintain 250 kts. It is less than a minute from start of roll and already 435 US gallons of fuel have been used.


Speedbird 2, contact departure, so long.

Turning through heading 235\xb0M, the F/E quickly re-applies full dry power as you pitch up to 17\xb0 to maintain 250 kts, but simultaneously reduce the left bank to 7.5\xb0, in order to increase both the radius of turn (to stay on the optimum noise abatement track) and the rate of climb (less bank, higher RoC).

On climbing through 2,500 ft you increase the bank angle back to 25\xb0 left bank and as you approach the 253\xb0 radial JFK, you hear 3-2-1 Noise from the F/O for the second time. The F/E actions the second noise-abatement power cut back, you pitch down to 12\xb0 and, if not in cloud, sneak a quick peek out of your left hand window, looking for the car park by the Marine Parkway bridge, as you would ideally like to pass right over the car park, if possible, as we tip-toe quietly across the Rockaway Beaches, in order to minimise the noise impact on the residents.

Keep the left turn going and intercept the 176\xb0 radial outbound from CRI, and at 5 miles DME from CRI, call for the F/E to slowly re-apply full climb power as you pitch up to maintain 250 kts. We are still in US territorial airspace, below 10,000 ft, and subject to statutory speed control.


Speedbird 2, present position direct to SHIPP, climb FL230, no speed control.

The F/O selects direct SHIPP in the INS and tells you that she has selected that information into your Flight Director. Having checked that the gear lever is at neutral, you call for the Nose Up , and then the Visor Up . Flight deck noise levels drop dramatically as the Visor locks up. Now more than 12 miles away from the coast, we are clear of US speed control requirements so lower the attitude to 9\xb0, accelerate to V MO , currently 400 kts, and ask for the After Take Off Checks.


Speedbird 2, present position direct to LINND, climb in the block FL550-600, accelerate Mach 2.0

Call for the Climb Checklist at Mach 0.7, which will trigger the F/E to start pumping fuel rearwards to move the CG aft, then when he's done that, straight into the Transonic Checklist . Maintain 400 kts IAS, and around 24,500 ft, at M0.93, ask for the re-heats back on, in pairs, and raise the nose by 3\xb0 to maintain 400 kts as they kick in.

Precise, smooth flying is required through the high drag transonic region, as the mach meter creeps up towards Mach 1. A sudden flicker on the VSI and Altimeter confirms that the shock wave has just passed over the static ports, and the aircraft is now supersonic. A quick glance at the elapsed time indicator shows that you\x92ve been hand flying for just over 9 minutes since the start of the take off roll.

Another fun start to a day in the office, and to think we got paid for doing it!


Best Regards

Bellerophon

Basically because we operated the Concorde at full throttle all the time except for noise abatement until decel / descent. The schedules and ratings fine tuned the full throttle performance according to a tightly tuned regeme - and reheat was selectable on switches rather than throttle lever angle because we spent most airborne time supersonic at full (dry) power without reheat. At the time that was the unique achievement of Concorde: reheat was used for a tiny proportion of the flight and so was relegated to four little switches. It wasn't even used for a go-around. Even on three. But that's another story.

Let's be clear folks, Concorde would have never operated to JFK without a very generous interpretation of the applicable noise abatement rules by the FAA/PoNYA guys who signed it off. Who else has ever approved a 30 degree banked turn initiated at 100' on departure as an SOP on a heavy aircraft??

Concorde had that 'je ne sais quoi' that encouraged airplane people everywhere to think big and ask themselves 'what can be done?'.

Correct me if I'm wrong, but I do not remember anybody ever whining (at least in print) about the significant premium revenue traffic diverted from the competing US airlines!

Of course, if the Yanks had actually produced an SST, things might have been very different.

With respect, that sounds more like the sort of climb rate associated with noise abatement rather than full power. Brian Calvert quotes 250 kts/2000ft/1000fpm/12deg attitude/reduced thrust for this. At 8000ft/400 kts/dry climb thrust he quotes 3000fpm, which is more the sort of number I would have expected (it is all a long time ago ......)

Could I ask a performance question of you folks?

I was watching the ITVV Concorde program the other day and a couple of things really stood out. The noise abatement take off from JFK looked pretty alarming from a climb rate point of view, looked like the aircraft tottered over the coastline with a pretty low rate of climb compared to the subsonic stuff. That being said she was supersonic 12 minutes after the thrust levers were advanced so she could certainly pick up her heels.

So the question is, if you were operating the aircraft out of somewhere with no climb or noise abatement restrictions (BGI?) on an average day with make take off weight what would be the typical time to M1? Course the 7 year old in me also want to know what the fastest time was that you saw on a revenue trip.

IIRC (somebody else can confirm?) that's right.
It was a JFK-LHR BA Concorde which landed at Cardiff (in Wales) with some kind of tech problem. The paxs were ferried to LHR and the repairs were done at Cardiff.
Then the a/c was flown back to LHR. Since the take-off was over the sea (so no noise abatement needed), and the plane was empty, with only little fuel, she went "like a scalded cat" and hit Mach 1 in about 6 minutes.

Mr Hoppy ,
I am aware it doesn't quite answer your question... I hope one of the pilots can answer that. But I doubt they would normally have kept specific records.

CJ

Although the Concorde site describes them as slats, the LE changes were a simple LE droop as shown in the Concorde 'B' site sketch.

The intention was to give some forward facing area (at low speed) so that the LE suction had something to work on and give "LE thrust". The AoA for vortex generation would have been delayed, but the net effect was to reduce TO drag and hence power required in noise abatement climb. For cruise the LE went back to its normal position of course.

The original prototype had a similar LE droop to the Concorde 'B' (but a bit less extreme). It was changed when it was found that the droop generated an underwing vortex at low AoA (towards zero 'g') at supersonic speeds and that this vortex went down the intake with unpleasant effects on engine face distortion. This could be avoided with the moveable LE.

I entirely agree with John Farley's comments. We were planning to fit canards on the second generation SST for exactly those reasons - they also gave a slightly better L/D in take-off climb which was useful for noise abatement, but they only just earned their keep in terms of economics!

Just for theories sake, if there were no noise, speed or boom considerations what would be the optimum profile for Concorde to fly after departure ?



In normal service I understand it had to comply with normal noise abatement departures, speed limits and remain subsonic until far enough from land to prevent the boom being a consideration.


But what if it could accelerate immediately, with no restrictions of any kind ?


I imagine you would stay in afterburner, accelerate to VMO and on to M2 in the climb ? or would airframe heating at lower altitudes prevent this ?



Lastly, was this ever done in testing, or for example leaving Barbados ?