Visor and droop nose (Part 1)

Concorde is especially recognized thanks to its mythical droop nose, we will try to explain simply "How it works"

The nose is drooped to improve the pilot's visibility during landing and take-off.

The high position gives the aircraft an aerodynamic shape suitable for supersonic flight.

The visor provides protection for the windshield against kinetic heating.

The different positions of the nose and the visor during each phase on the ground and in flight:

The only difference between the SA and production aircraft is the angle in the down position. In fact, on the SA, the nose can descend to 17.5 degrees, while for production aircraft; the angle of the nose in the down position has been limited to 12.5 degrees.

Late in the Concorde program, when the first two pre-production planes made their first flights, the two remaining customer companies, Air France and British Airways, found that in the low position, the pilots no longer saw the nose, and therefore the reference visual they had on other conventional aircraft.

It was therefore decided to test in flight a new configuration on the aircraft 01 (G-AXDN) the brother of the SA, the nose system being British responsibility. The only possible configuration, and not requiring major technical modifications afterwards, was to have the nose in the low position at an angle of 12.5 degrees. Indeed, the two sets of jacks installed side by side on the Concorde built at that time (the first two production planes included) consisted of two bodies, one for a travel of 5 degrees, one for a travel of 12.5. degrees.

For this, the nose of 01 was first lowered to 17.5 degrees, then the 5 degree jacks were raised (thanks to a modification of the electrical wiring and a control switch), which made it possible by subtraction to obtain an angle of 12.5 degrees.

Once this configuration was validated during flight tests, the technical modification at the manufacturer of the jacks (the French DBA Air-Equipment) was to modify the end-of-stroke limit of the 12.5 degrees body to obtain a travel of 7.5 degrees. These jacks were installed on the first two production planes, then of course on the following planes.

Control lever

To operate the visor and the droop nose, the control is located on the dashboard.

As already shown in a previous article, this control lever was absent in the SA when it arrived in 1988 and it was our friend Boramy who made us the above replica.

Normal running

The visualization of the movements and positions of the nose and the visor are indicated right next to the control lever.

Here are the indications according to the positions of the lever.

In high position UP and first step down visor.

In VIS / 0 ° position, nose down to 5 degrees.

Position 5 ° nose down to 17.5 degrees

DOWN nose position at 17.5 degrees.

The normal control of the droop nose and the visor is powered by the GREEN hydraulic system.

Standby operation

In the event of a failure of the GREEN system, the visor and the nose can be lowered in backup mode by the YELLOW hydraulic system.

3 switches individually allow:

- Lower the visor and isolate the normal control

- Lower the nose to the 5 degree position

- Lower the nose to the 17.5 degree position

Emergency operation

In the event that the green and yellow hydraulic and / or electrical systems are unavailable, the visor and nose may be lowered in emergency by gravity.

A mechanical system via an emergency release handle allows to unlock the upper hook of the nose which descends by gravity and by aerodynamic pressure, to the 5 degree position only.

When the nose begins to descend, it pushes on an axis which unlocks the top of visor’s uplock which also descends in the low position by gravity.

This emergency release handle was removed from the SA by Air France when the plane arrived at Orly in 1976 (certainly to prevent accidental unlocking)

Operation details

A hydraulically operated lock (unlocking only) secures the visor in the up position. Two identical locks keep the nose in the up position, and collet locks in the nose cylinders keep it in the 5 degree position when there is no more hydraulic pressure.

Hydraulic pressure keeps the nose low.

A red alarm indicator lights up:

- if the nose or the visor are unlocked

- or in transit from one position to the next

- or if one of the collet locks is not engaged when the nose is at 5 degrees.

An electrical security in the wiper / windshield circuit prevents the visor from being raised when the wipers are not in the "PARKING" position.

If, in the event of failure of the security, the visor does not work when the windshield wipers are on "PARKING", the prohibition can be overridden to allow the visor to be raised.

CHARACTERISTIC VALUES

Oronite M2-V hydraulic fluid

Hydraulic circuit pressure 4000 p.s.i. (pounds per square inch)

1000 P.S.I. = 68.969 bar

4000P.S.I. = 275,576 bar = 110 times the pressure of a car tire.

Manoeuvre time:

Visor raising or lowering (normal or emergency): 4 to 8 seconds

Visor lowering (emergency): 15 to 25 seconds

Droop nose lowering 5 degrees (normal}: 2 to 5 seconds

Lowering of the low position (production aircraft): 4 to 5.5 seconds

(Emergency) 60 seconds maximum

Up to 5 degrees (production aircraft): 4.5 to 6.5 seconds