CONCORDE SST  

6. AIRCRAFT INFORMATION

6.1 Airframe

6.1.1 Information (see appendix 1)


6.1.2 Maintenance

The aircraft had undergone a scheduled check AO1 in accordance with the approved maintenance programme. The check commenced on 17 July 2000 and was completed on the 21st. During the check, the left main landing gear bogie had been replaced in order to correct an acceptable deferred defect related to the under-inflation detection system.
Since the A check, the aircraft had undertaken four flights, on July 21, 22, 23 and 24. On the 24th, several maintenance operations had been carried out:
Problems Maintenance Actions
Slight thrust surges in cruise at mach 2, with illumination of start pump warning light. Checks on both TCU¹s, replacement of the N1 limit amplifier, check on the EGT line, ground test OK.
Brake overload warning light for wheel n° 4. Cable changed.
Slow leak in blue hydraulic system in flight. Connecting joint on the artificial feel cylinder on the blue hydraulic system replaced.
Tyre on wheel n° 5 worn. Wheel n° 5 replaced.

The aircraft was originally planned as a reserve for 25 July. F-BVFA was planned to carry out scheduled flight 002 in the morning and F-BVFC to undertake Flight 4590. For maintenance reasons, there was an allocation change between F BVFA and F-BVFC. F-BVFA was finally declared unavailable during the night and the reserve aircraft, F-BTSC, was programmed in its place to carry out Flight 4590.

The aircraft was airworthy and there were no acceptable deferred defects for Flight 4590. Prior to the flight, the GARRETT pneumatic motor which activates the engine n° 2 secondary exhaust nozzle buckets, had been replaced. Tests had been carried out and they revealed no anomalies.

6.2 Landing Gear

6.2.1 General

The Concorde has a nose gear, an auxiliary gear situated at the rear of the fuselage and two main landing gears, each with a bogie with four wheels. The bogies are equipped with a system which detects under-inflation of a tyre and transmits a visual signal to the cockpit. This detection system is inhibited when the speed of the front wheels is less than 10 kt or when the indicated airspeed is above 135 kt.

6.2.2 Gear Retraction

Gear retraction is controlled electrically by the landing gear control lever situated on the pilot¹s panel (three-position lever: up, neutral, down) and is activated by hydraulic pressure from the Green circuit (see figure 1). The lever cannot be moved from the "neutral" position to the "up" position unless the left main landing gear shock strut is no longer compressed.

Conditions for gear retraction:

When all of the landing gear is locked in the "up" position, the gear doors close. During retraction of the main gear, the shock struts are retracted into the gear leg to allow them to fit in the gear well. The wheels are automatically braked when the gear selector is in the "up" position.

For the landing gear, the Yellow hydraulic circuit is used only if there is a failure in the Green circuit. The perpendicularity of the gear is ensured by two autonomous nitrogen-powered pneumatic actuators


Figure 1. Synoptic diagram of the main gear hydraulic system


6.2.3 Braking

The brakes are manufactured by Dunlop. Braking is electrically controlled and is activated by hydraulic pressure from the Green circuit in normal conditions.

In case of failure in the Green circuit, an automatic switch allows the Yellow circuit to be used. In case of emergency braking, only the Yellow circuit is used in direct hydraulic liaison with the rudder bars.


Figure 2. Synoptic diagram of main landing gear braking


6.2.4 Deflectors

The deflectors are made of composite materials and fibreglass (to make them frangible) except for the bogie fasteners. Each deflector weighs around 4 kg and is located at the front of each main landing gear. Their function is to deflect water and spray to ensure it does not enter the engine air intakes. These deflectors were the subject of an optional Service Bulletin (SST 32-103 of 12/01/95 modified on 28/02/95) which proposed the insertion of two cables in the leading edge in order to retain pieces of the deflectors in case of failure. Air France did not apply the aforementioned Service Bulletin.


6.2.5 Wheels and Tyres

The wheels were manufactured by Dunlop, and the tyres used by Air France were manufactured by Goodyear in the United States. No retread tyres have been used since 1997.

On the day of the accident, the main landing gear wheels and tyres on F-BTSC were installed as follows:


Figure 3 (from above)
WHEEL P/N WHEEL S/N Position on aircraft Workshop issue date Date installed on aircraft TYRE S/N Number of cycles
AHA1216 531 1 09/06/00 10/07/00 91510047 9
AHA1216 579 2 25/05/00 29/05/00 91831651 37
AHA1216 594 3 10/05/00 18/05/00 91801029 45
AHA1216 500 4 17/02/00 22/06/00 91831659 23
AHA1216 446 5 06/07/00 24/07/00 91560078 0
AHA1216 581 6 12/07/00 18/07/00 91570604 4
AHA1216 518 7 22/06/00 24/06/00 91870259 19
AHA1216 591 8 04/07/00 09/07/00 91930448 9

N.B. notation in bold type refers to left main landing gear.

6.3 Fuel

The signal from each fuel gauge is sent simultaneously to the corresponding indicator and to a totaliser. By design, error in measurement of the total fuel quantity must not exceed 5 % in extreme flight conditions, and the error in measurement on each of the tanks must not exceed 2 %. The quantity of fuel present in a tank can be considered to be correctly indicated when the reading is greater than zero. The quantity present cannot be presumed if the above does not apply.

Note: a general electrical power cut fixes the last indication supplied by the needles and masks the indications on the rollers with a flag. The failure of an electrical connection from a fuel gauge leads to an indication of zero on the corresponding indicator.

Before the accident flight, the tanks had been filled with jet fuel (Jet A1). An overfill of 300 litres, equivalent to a quantity of 237 kg had been added. In total, the quantity loaded was around 94 800 kg.

Note: the overfill procedure allowed loading of a maximum of 1 630 litres extra, compared to the quantities mentioned below.

The capacity of the thirteen tanks is presented in the table below. These represent maximum capacities without exceeding the level of the upper sensors.

Function Number Capacity (litres) Quantity (kg) density=0.792
Engine supply 1
2
3
4
5 300
5 770
5 770
5 300
4 198
4 570
4 570
4 198
Main tanks 5
6
7
8
9 090
14 630
9 350
16 210
7 200
11 587
7 405
12 838
Auxiliary tanks 5A
7A
2 810
2 810
2 225
2 225
Transfer tanks (balance) 9
10
11
14 010
15 080
13 150
11 096
11 943
10 415
Total
119 280 94 470


6.4 Engines

6.4.1 General

Power is supplied by four twin spool turbojets installed in pairs, each being equipped with a reheat, a variable area air intake and variable primary and secondary exhaust nozzle used to optimise performance. The secondary exhaust nozzle also incorporates the thrust reverser.

The no. 1 and no. 2 engines are respectively the outer and inner left engines, engines no. 3 and no. 4 the inner and outer right engines.

Manufacturers: Rolls Royce and SNECMA.


no. 1 no. 2 no. 3 no. 4
Serial number CBE031 CBX115 CBE092 CBE051
Installation date 03/02/2000 01/08/1999 14/06/2000 23/08/1999
Total hours 11 200 9 158 8 394 11 670
Hours since installation 342 576 84 576
Cycles since installation 106 181 28 181

6.4.2 Contingency Mode

The contingency mode can be activated manually or automatically in the case of engine failure on takeoff. Thrust above the maximum takeoff thrust can then be provided by remaining engines. Automatic mode is activated when:

The power of the other three engines then increases automatically up to a level which may reach 105 % of N2.



6.4.3 Reheat Cutout

As soon as an engine¹s N1 falls below 75 %, reheat on that engine is disconnected. Reheat is re-activated when N1 exceeds 81 %.

6.4.4 Fire Protection

Fire detection on an engine is ensured by two loops which react to increases in temperature. They are made up of four components assembled in line so as to detect:

If only one loop detects a fire, the loop is indicated as faulty and has to be shut off by the crew. If both loops detect a fire, the Gong sounds and the appropriate red ENGINE warning light comes on in the Main Warning System (MWS) panel, followed by a flashing red warning light on the engine shutdown/fire handle of the corresponding engine and an aural warning (bell).

Pulling the engine shutdown/fire handle shuts:

The dual head extinguishers are activated by two push buttons located behind each engine shutdown/fire handle.

Note: the red warning light in the Main Warning System is also associated with alarms for low oil pressure, engine TCA overheat, and detection of liquid in the dry bays.


6.4.5 Engine Maintenance


Each engine consists of twelve modules whose maintenance is undertaken by Air France, by SNECMA Services or by GEAS. The final assembly is performed by GEAS.
Tasks performed can be of three types: visual inspection, partial repair or major repair based on the Olympus Maintenance Manual.

Readings taken by the FE during supersonic flight of parameters such as EGT and FF assist in assessment of engine condition. The readings from these engines on previous flights have not revealed any malfunctions.

6.5 Weight and balance

6.5.1 Weight

The weights listed in the first table hereafter are those which were entered by the Dispatcher to establish the forecast weight, then the final weight. The second table shows the real weights as established by the investigation.

Computer-generated weight (kg) Phase 1
forecast
Taxi weight Takeoff weight
Corrected basic weight 81 560 81 560 81 560
Baggage 1 651 2 131 2 131
Fuel
+ taxiing
93 400
+ 2 000
92 936
+ 2 000
92 936
Passengers 8 253 8 253 8 253
EIC 0 0 0
Total weight 186 864 186 880 184 880
Real or noted weight (kg) Phase 1
forecast
Taxi weight Takeoff weight
Corrected basic weight 81 560 81 560 81 560
Baggage 1 651 2 525 (1) 2 525
Fuel + taxiing 39 730
( before refuelling)
94 853 93 853 (4)
Passengers 8 253 (2)
7 759 (3)
8 253 (2)
7 759 (3)
8 253 (2)
7 759 (3)
EIC 60 (5) 60 60
Total weight
187 251 (2)
186 757 (3)
186 251 (2)
185 757 (3)

notes

(1) Nineteen items of baggage loaded on board were not taken into account, only 103 items appearing on the load sheet. There were 122 items of baggage loaded on board, with an average estimated weight of 20.7 kg each, making a total of 2 525 kg.

Note: these items of baggage had not been taken into account by the Gaétan system nor by the Baggage Reconciliation System (See paragraph 16.2).

(2)   By applying the fixed average for passengers: one passenger = 84 kg, one child = 35 kg.

(3)   By applying the fixed average for men and women: one man = 88 kg, one woman = 70 kg, one child = 35 kg.

Note: for holiday charter flights, it is also possible to use a fixed average of 76 kg per passenger.

(4)   Allowing that the aircraft consumed a ton of fuel during taxiing.

(5)   The EIC corresponds to 60 kg of newspapers.


6.5.2 Balance

The CG noted on the final load sheet gives a figure of 52.3 % at Zero Fuel Weight and 54.2 % for taxiing with fuel; this is the normal CG for a takeoff at maximum takeoff weight.


6.6 Takeoff Performance


The following parameters are used hereafter for performance calculations:

The Operating Manual provides the maximum structural weights:

Since the wind readings at different test points show a light and variable wind, the calculations are made with calm wind conditions.

Note: the takeoff limitations evaluation gives a maximum performance weight of 186.7 tons. With this weight and the associated speeds (V1, V2, VR), the second segment limitation and the tyre limitation have to be taken into account. The higher the aircraft speed on takeoff, the further the second segment limitation is pushed back. However, this speed is further limited by the constraints imposed by the tyres.

At the maximum structural weight at takeoff, the calculations provide the following values:

The Flight Manual provides the following zero rate of climb (VZRC) figures.

VZRC (kt) 185 t 3 engines 2 engines
Gear retracted 193 262
Gear extended 205 >300

Note: the notion of VZRC is important for Concorde. It is the cruising threshold speed, which allows the aircraft to remain in level flight at zero rate of climb. On a thrust/speed diagram, VZRC is located at the intersection of the thrust available curve and the thrust required curve. These points represent an unstable condition. Furthermore, these speed values are highly influenced by the actual weight of the aircraft.

Ground and air minimum control speeds:

Takeoff runway length required and takeoff distance required (Flight Manual):

Note: These distances are regulated distances taking into account the failure of one engine.

A calculated simulation can be performed based on these parameters and a serviceable aircraft with four engines operating. Since it is not possible to know the exact weight at brake release (because of utilisation of the average passenger weights, for example), the maximum structural weight at takeoff (185.070 kg) is used for the calculations.

The results of this simulation are as follows (rounded figures):

For all of these values, the influence of an increase in weight of one ton was examined and found to be negligible.