Aircraft Crash in Moscow
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So far I have not seen any evidence that the brakes were 'not working', just that they did not appear to be able to stop the a/c. Circumstantial evidence so far points to a relatively high forward thrust for whatever reason, be it the previous 204 reverse lever mechanical failure as posted by Kulver or perhaps a g/a attempt - or do we have another Congonhas?
I cannot seriously believe that anyone could put a 'computer' between the pedals and the brake cylinders other than an anti-skid system (which can be deselected) in ANY aircraft.
I cannot seriously believe that anyone could put a 'computer' between the pedals and the brake cylinders other than an anti-skid system (which can be deselected) in ANY aircraft.
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WOW switches doesnt prevent wheel brakes (main and emergences) from engaging. Only they prevent AUTObraking and AUTOreverse function and interceptors opening. Brakes are unblocked by wheels spinning signal (more than 150 kmh).
Greasing of WOW switches will not prewent malfunction, because it is caused by moisture penetrated into their inside through weared or defective rubber membrane and freesed opening of the normally closed contacts. In case of normally opened contacts force from WOW links can break ice on contacts and close even faulty switch, but removing force from contacts in case they are frosen can't open them.
There is two WOW swithes on every strut - on cylinder and on trolley.
All information from forumavia and aviaforum ru
2BOAC - latest directive isn't about WOW switches (which was sent day BEFORE accident), it's about swithing off thrust in case of reverse malfunction to prevent landing with engines on full throttle (look at 2009 report and Novosibirsk overrun case).
Avherald:
Greasing of WOW switches will not prewent malfunction, because it is caused by moisture penetrated into their inside through weared or defective rubber membrane and freesed opening of the normally closed contacts. In case of normally opened contacts force from WOW links can break ice on contacts and close even faulty switch, but removing force from contacts in case they are frosen can't open them.
There is two WOW swithes on every strut - on cylinder and on trolley.
All information from forumavia and aviaforum ru
2BOAC - latest directive isn't about WOW switches (which was sent day BEFORE accident), it's about swithing off thrust in case of reverse malfunction to prevent landing with engines on full throttle (look at 2009 report and Novosibirsk overrun case).
Avherald:
On Dec 29th 2012 it became known after another TU-204 overran the runway at Moscow Vnukovo, see Accident: Red Wings T204 at Moscow on Dec 29th 2012, overran runway on landing, that on Dec 28th Rosaviatsia had alerted the aircraft manufacturer Tupolev of a brakes malfunction as cause of the overrun at Novosibirsk. In a letter dated Dec 24th 2012 Rosaviatsia demanded with reference to this overrun that all operators of Tupolev TU-204 should perform an extra lubrication to grease the drive mechanism limit switches that are crimped onto the main landing shock absorber before next departure.
On Dec 31st 2012 Rosaviatsia released a modification to aircraft operations manual requiring flight crew to apply reverse thrust only if the engine is operating (stating application of reverse thrust is prohibited on a malfunctioning engine). To apply reverse thrust the engine should be pulled to idle for 1-2 seconds, then command reverse thrust at minimum thrust, verify yellow "thrust reverser unlocked" followed by green "REV" indications appear, only then apply high reverse thrust. Rosaviatsia reported there have been a number of cases where the green "REV" indication did not appear (editorial note: there have been rumours since this overrun, that the crew had applied reverse thrust, the reverser however had not opened and at least one of the engine was delivering full forward thrust instead).
On Dec 31st 2012 Rosaviatsia released a modification to aircraft operations manual requiring flight crew to apply reverse thrust only if the engine is operating (stating application of reverse thrust is prohibited on a malfunctioning engine). To apply reverse thrust the engine should be pulled to idle for 1-2 seconds, then command reverse thrust at minimum thrust, verify yellow "thrust reverser unlocked" followed by green "REV" indications appear, only then apply high reverse thrust. Rosaviatsia reported there have been a number of cases where the green "REV" indication did not appear (editorial note: there have been rumours since this overrun, that the crew had applied reverse thrust, the reverser however had not opened and at least one of the engine was delivering full forward thrust instead).
Last edited by Kulverstukas; 1st Jan 2013 at 08:42.
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Thanks Kulver - I had 'noted' that. If I understood your previous info from the other accident the crew physically 'broke' the reverse mechanism and caused a high forward thrust? Does anyone know how the reverse selection on the 204 is made?
Capt Inop - are you going to 'revise' your post about reversers+g/a ie "when you go balls to the walls for a GA." or does your airline have different operating restrictions to Boeing and AB?
Capt Inop - are you going to 'revise' your post about reversers+g/a ie "when you go balls to the walls for a GA." or does your airline have different operating restrictions to Boeing and AB?
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Yes, tabs marked РЕВЕРС in front of the main levers.
It's TO, but you can see throttles operation:
and here at 2:11
It's TO, but you can see throttles operation:
and here at 2:11
Last edited by Kulverstukas; 1st Jan 2013 at 10:09.
(editorial note: there have been rumours since this overrun, that the crew had applied reverse thrust, the reverser however had not opened and at least one of the engine was delivering full forward thrust instead).
There were a couple of past instances where Learjet 60 pilots deployed reversers, the balk solenoids released the T/R sub levers, reverse thrust was applied (spool-up) but then the WOW switch continuity was lost. In one case a deer was collided with during landing and in the other a tire blew during takeoff and took out the switch followed by an ill-advised RTO. In both cases the loss of WOW continuity resulted in reverser auto-stow. But with the T/R sub levers already past the balks, engine thrust remained very high.
In the deer collision case the pilot stowed the sub levers and stood on the brakes resulting in a low-speed overrun. In the high-speed RTO case full braking had little effect against very high forward thrust and pilot indecision resulted in a high speed excursion across a road and into an embankment.
I don't know what if any relation the sequence of events in the Lear instances have to this accident but the above quoted "rumor" reminded me of them.
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Capt Inop - are you going to 'revise' your post about reversers+g/a ie "when you go balls to the walls for a GA." or does your airline have different operating restrictions to Boeing and AB?
going around after selction of Reverse is prohibited
Capt. Inop., Selecting Idle Reverse is selecting reverse. The reason for the banning of G/A's after Reverse selection is not due to spool-up times/forward thrust, whatever, etc etc. It is due to the possibility of a reverser door not stowing during your aforementioned fire-walling for a G/A.
Please, in future, select whatever reverse setting you need for the particular conditions. Not because the brakes have bitten or not.
@ BOAC: Yes. Quite.
Capt. Inop. Does your company say anything about rapidly stowing the thrust reversers? I.e. go easy! The engines are producing forward thrust but the airflow is redirected forwards. Quickly stowing them from full reverse will give you a jolt up the.....
Not to worry. Awaiting the report.
Capt. Inop. Does your company say anything about rapidly stowing the thrust reversers? I.e. go easy! The engines are producing forward thrust but the airflow is redirected forwards. Quickly stowing them from full reverse will give you a jolt up the.....
Not to worry. Awaiting the report.
Last edited by sprite1; 1st Jan 2013 at 13:04.
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Quickly stowing them from full reverse will give you a jolt up the
Having flown the DC9, MD80 and the B737 up in the arctic for many years with snow covered runways and sometimes very poor friction selecting forward thrust from idle reverse have happend a few times to take it back into the air again.
Last edited by Capt. Inop; 1st Jan 2013 at 13:53.
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the possibility of a reverser door not stowing during your aforementioned fire-walling for a G/A
They blew engine Nr. 2 and almost ran of the end.
Had the reversers om nr2 stowed it would have been a normal GA.
Yes Capt. Inop. I've had the pleasure of the JT8D's too. The principle is the same with any engine with moving parts. They could fail.
Take one of your successful G/A's. What would've happened if one bucket failed to stow? You would not have got airborne but would have overrun at a higher ground speed than if you'd just left idle/max reverse out and rolled off the edge.
Your procedure is wrong. Seriously.
You're not acknowledging that the ban is there too stop a failed door stow scenario.
Take one of your successful G/A's. What would've happened if one bucket failed to stow? You would not have got airborne but would have overrun at a higher ground speed than if you'd just left idle/max reverse out and rolled off the edge.
Your procedure is wrong. Seriously.
You're not acknowledging that the ban is there too stop a failed door stow scenario.
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I'm not T204 pilot, so can only help with translation from flight manual:
October 1/04
74.08.0000000 RLE
Flight manual, Tu-204-300
OPERATING SYSTEMS AND EQUIPMENT - Engines
PS it's 204-300 FM, 204-100 can have different control layout.
October 1/04
74.08.0000000 RLE
Flight manual, Tu-204-300
OPERATING SYSTEMS AND EQUIPMENT - Engines
(2) The engine control throttle levers are located on middle isle. Automatic operation of the engine is the controlled by thrust control unit VSUT-85 (Thrust Control Computer).
To avoid the possibility of a kickback there is the throttle brake.
When VSUT is switched ON with throttles blocked on IM#2 displayed "UNBLOCK THROTTLE".
On the throttle lever there is inbuilt devices which disable VSUT by applying 1.5 - 2 kg force to the handle.
Buttons are located on the throttle manually activate high thrust (PR), see Fig. 8.1.10.
Modes of operation of the engine and the corresponding throttle position are shown in Table 8.1.1.
8.1.1.2 The system of reverse thrust
(1) Reverse device and its control units mounted on the engine and are designed for reverse thrust.
Return (negative) thrust is created by changing the air flow direction
by opening or closig the flaps of reversing device. Flaps can be set
in one of two positions: DIRECT THRUST or BACK THRUST.
Shifting of the flaps is made by hydraulic cylinders, which pistons
are connected to the control lever mechanism.
...
(2) The thrust reverser controlled by pilots with Reverse Control Levers (RCL)mounted on the Throttle Levers (TL).
Before turning on the reverser, throttle is moved to IDLE, RCL in the lower
(Off) position is fixed by latch. The reverse thrust value is determined by the RCL up position similarly to TL position when managing direct thrust.
To enable small reverse thrust RCL must be removed from the latch by pressing the RCL lever head down and move lever to the intermediate stop (small reverse).
To enable maximum reverse bring RCL all the way to the "maximum reverse" stop.
(3) Reverse control light signal device is located on the Pilots instrument panel:
- REVERSE LOCK is yellow;
- REVERSE ON is green.
In addition, information on operation is on the IM#2, in the frame
ENG / SIGN (ENG MAIN, ENG GEN):
- When reverse lock is open - LOCK (yellow);
- When the reverse is ON - REV (green).
To avoid the possibility of a kickback there is the throttle brake.
When VSUT is switched ON with throttles blocked on IM#2 displayed "UNBLOCK THROTTLE".
On the throttle lever there is inbuilt devices which disable VSUT by applying 1.5 - 2 kg force to the handle.
Buttons are located on the throttle manually activate high thrust (PR), see Fig. 8.1.10.
Modes of operation of the engine and the corresponding throttle position are shown in Table 8.1.1.
8.1.1.2 The system of reverse thrust
(1) Reverse device and its control units mounted on the engine and are designed for reverse thrust.
Return (negative) thrust is created by changing the air flow direction
by opening or closig the flaps of reversing device. Flaps can be set
in one of two positions: DIRECT THRUST or BACK THRUST.
Shifting of the flaps is made by hydraulic cylinders, which pistons
are connected to the control lever mechanism.
...
(2) The thrust reverser controlled by pilots with Reverse Control Levers (RCL)mounted on the Throttle Levers (TL).
Before turning on the reverser, throttle is moved to IDLE, RCL in the lower
(Off) position is fixed by latch. The reverse thrust value is determined by the RCL up position similarly to TL position when managing direct thrust.
To enable small reverse thrust RCL must be removed from the latch by pressing the RCL lever head down and move lever to the intermediate stop (small reverse).
To enable maximum reverse bring RCL all the way to the "maximum reverse" stop.
(3) Reverse control light signal device is located on the Pilots instrument panel:
- REVERSE LOCK is yellow;
- REVERSE ON is green.
In addition, information on operation is on the IM#2, in the frame
ENG / SIGN (ENG MAIN, ENG GEN):
- When reverse lock is open - LOCK (yellow);
- When the reverse is ON - REV (green).
Last edited by Kulverstukas; 1st Jan 2013 at 16:05.
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Thanks - so like the Boeing, the reverse N1 is controlled by the RCL position. The question remains now what happens if the reversers do not unlock? Are the RCL's locked 'inop'? If any reverser safety lock is over-ridden, can N1 be increased in forward thrust? On a Boeing, the reverser levers are mechanically locked down until reverser deployment and it would be very difficult to increase N1 until then.
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Kulverstukas...
Firstly. Grateful for the wealth of info you supply.
I am sure it is operator specific? Perhaps not?
Is "Cycle Reverse Doors" on the pre push CL? I'm sure it is, since they may soon become necessary, even crucial, for RTO?
Firstly. Grateful for the wealth of info you supply.
I am sure it is operator specific? Perhaps not?
Is "Cycle Reverse Doors" on the pre push CL? I'm sure it is, since they may soon become necessary, even crucial, for RTO?
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Lyman, the book I make translation from is issued by Tupolev and was found by link from some forum I read about accident.
Your second question I can't answer, sorry
Your second question I can't answer, sorry
Last edited by Kulverstukas; 1st Jan 2013 at 16:19.