Rudders, Elevons, Power Flying Control Units (PFCU)
Concorde is controlled in pitch and roll by 6 elevons, and in yaw by 2 rudders. The pilots control column movements are the same for Concorde as in any other aircraft. Unlike other aircraft Concorde has no tail-plane and the elevons are placed along the trailing edge of the wing. The nose up and down movements, are controlled by these 6 elevons (mainly the inner pair). The middle and outer elevons pairs also act as ailerons.
Concorde uses a ‘fly-by-wire’ system in which the pilot’s control column movements are conveyed to the hydraulic Power Control Units (PFCU’s) by electrical signals (Concorde was the first passenger jet to have fly-by-wire). Concorde can also be flown with the total loss of all electrical signals to the elevons because there is a direct link, after electrical failure, between the control column and the elevons. Under these conditions flying Concorde would become more difficult, but with practice it can be flown safely in all situations.
Conventional trim is provided in pitch, roll and yaw. An electric trim system is provided in pitch only and is controlled directly by the pilot using the pitch trim selector on each control column.
Hydraulic power to the 8 PFCU’s is provided by either the Green or Blue hydraulic system, this is selected from the servo control panel on the flight deck over head panel, there is a Yellow hydraulic standby system available for use if required in an emergency.
Green, Blue and Yellow hydraulic systems are powered by engine-driven pumps at a pressure of 4,000psi. The hydraulic system is distributed across all 4 engines to offer complete redundancy. The Green system is run from engines 1 and 2, the Blue system from engines 3 and 4 and the standby Yellow system from engines 2 and 4.
The PFCU’s end stops allow the inner elevons a 9 degrees of travel up or down and the outer/middle elevons can travel 23.5 degrees up or down. The end stops on the rudder allow a travel range of 30 degrees in either direction. The actual travel limits, that are controlled by the fly-by-wire mixing unit, are a little less that these mechanical maximums.
To work the PFCU’s they are fed with hydraulic fluid, pressurized to 4000psi by engine driven pumps which is why a parked Concorde usually has its elevons hanging down, the power being off, and gravity has taken over
Pitch & Roll
In pitch the elevons all work together, in roll the two sides move opposite directions
Pitch – Left and right elevons up
Roll – Left elevons down, right elevons up
Pitch and roll together-
left elevon pitch = up
Roll right = down
Resultant = level
The pilot does not move the elevons and rudder himself – the force involved are too great. Between the control column and the moving surfaces there is a system of motive power and a method of controlling the power. Click on ‘Fly-By-Wire’ for more information.