Device for assisting with retrimming an aircraft control

Details Device for assisting with retrimming an aircraft control Device for assisting with retrimming an aircraft control

1999-12-23

2001-08-21

Jordan, Charles T. (Department: 3644)

Aeronautics and astronautics

Aircraft control

Automatic

C244S236000, C244S221000

Reexamination Certificate

active

06276640

ABSTRACT:

The present invention relates to a device for assisting with retrimming an aircraft control.
It applies more particularly to an aircraft, especially a helicopter, comprising a flight-control device which comprises, in particular:
said control, for example, in the case of a helicopter, a collective pitch lever, a cyclic pitch stick or a rudder bar, which can be actuated by a pilot of the aircraft with a view to controlling a controlled member, particularly a servocontrol for the main lift and forward travel rotor or for the antitorque tail rotor, of the helicopter; and
a flight-assistance system which is connected to said control and which is intended to determine a command and apply it to said controlled member so that the action of said controlled member allows a flight parameter to be kept at a reference value. As far as said flight parameter is concerned, it may, in particular, be the attitude, speed, altitude, etc., of the aircraft.
In the context of the present invention, said flight-assistance system may be an electrical flight-control device or may include an automatic pilot.
It is known that, in the case of an aircraft fitted with an automatic pilot (with rams mounted in series in the flight controls and possibly parallel rams known as TRIM or compensating rams, connected to the computer of the automatic pilot), the latter, through a series ram, adds to the command generated by operation of the control, an additional command, the purpose of which is to maintain an objective, that is to say keep a flight parameter at a reference value. Said command and said additional command are then transmitted to one or more servocontrols of the controlled member
It is known that, in order to prevent an aircraft and particularly a helicopter from getting into a flight configuration from which the pilot cannot recover it, particularly in the event of an uncontrolled full stroke of the ram, the authority of the ram or rams used is limited to a few percent, generally to a value below 15%.
In consequence, because of this limited authority, it is often impossible, in practice, to maintain an objective of the aforementioned type without retrimming the control with a view to reducing the authority demanded of the flight-assistance system and therefore of the ram.
By way of illustration, consider a helicopter with an automatic pilot and flying at 10 km/h, the automatic pilot having the objective of maintaining a 10° nose-down attitude when accelerating up to 200 km/h, for example. Assuming that the control or stick remains stationary, to maintain a 10° nose-down attitude throughout the acceleration phase, the automatic pilot needs to add an increasing command to the pitch command in order to counter the static change in the command which is due to the increase in speed. The command that has to be added between 10 km/h and 200 km/h is of the order of a few tens of percent.
It is therefore not possible, for the automatic pilot associated with a series ram with authority limited to a few percent, to maintain such a 10° nose-down attitude up to 200 km/h, starting from 10 km/h
This problem can be solved by an appropriate displacement of the control so as to retrim it with regard to maintaining the aforementioned objective, that is to say, in the context of the present invention, so as to bring it into a position for which the command generated by said control allows the flight parameter in question (the nose-down attitude, in the aforementioned example) to be brought to the reference value or to a value close to it (10° in said example).
However, such a retrimming displacement demands work of the pilot, which work it was wished to avoid by action of the automatic pilot.
A system for the motorized displacement of the control, intended to displace the latter in order to retrim it, is known.
However, a known system of this kind has drawbacks, particularly:
it requires means (and, in particular, a motor) which are relatively bulky;
it is expensive; and
it contains numerous parts which are liable to break down.
The object of the present invention is to overcome these drawbacks. The invention relates to an inexpensive and not very bulky device for assisting a pilot of an aircraft in simply and effectively retrimming a control.
To this end, according to the invention, said device of the type comprising a flight-control device which comprises, in particular:
said control which can be actuated by a pilot of the aircraft with a view to controlling a controlled member of the aircraft; and
a flight-assistance system which is connected to said control and which is intended to determine an additional command and apply it to said controlled member so that the action of said controlled member allows a flight parameter to be kept at a reference value is noteworthy in that it comprises:
at least one first detection means for detecting the actual position of said control;
a calculation unit for determining the direction and magnitude of displacement of said control so as to retrim it, on the basis of said actual position detected by the detection means and a reference position of said control, corresponding to the latter being in the trimmed position with regards to keeping said flight parameter at said reference value; and
a display means capable of displaying to said pilot of the aircraft at least one characteristic sign indicating the direction and magnitude of the displacement of the control that is needed for retrimming it.
Thus, by virtue of the invention, the aircraft pilot knows precisely the direction and magnitude of displacement needed to retrim the control, with a view to reducing the authority demanded of the flight-assistance system, which makes it possible to retrim precisely and quickly and to overcome the aforementioned drawbacks.
Furthermore, as the retrimming action is performed manually and therefore requires no special-purpose (mechanical, hydraulic, etc.) means, the risk of breakdown, the bulk and the cost of the device according to the invention are very low.
In addition, the retrimming action which consists in simply displacing the control requires only a small amount of work on the part of the pilot.
Of course, the device according to the invention may be applied to an aircraft which has no system for displacing the control. However, it may also be applied to an aircraft which is fitted with a motorized displacement system like the aforementioned one. In this case, the device according to the invention can be made active either at the same time as said known system, possibly by providing means which give priority to one or other of them, or as a supplement for said system, to remedy breakdown thereof.
Incidentally, the device according to the invention advantageously comprises a means for minimizing or even completely inhibiting any change in said reference value of the flight parameter considered during manual action of retrimming the control, it being possible, for example, for such an action to be detected by a second special-purpose detection means so that the status of the aircraft changes as little as possible during retrimming. It is thus possible, during retrimming, to avoid a change in flight configuration which is likely to be brought about by a simultaneous change in the flight parameter and in the position of the control, such a change, of course, not being desired by the pilot who is then demanding only a retrimming action.
As a preference, said second detection means is formed in such a way as to detect at least one of the following parameters:
in the case of a control equipped with an anchoring means, the angular difference between the actual position and the anchored position of said control;
the force exerted by a pilot on the control; and
actuation by a pilot of a special-purpose actuating means intended to inform of the taking of manual retrimming action.
Furthermore, advantageously, the device according to the invention comprises a third means for reducing the authority demanded by the flight-assistance system during a manual retrimming action.
Furthermore, advantageous

Affiliated with

Also associated with

Rating

Device for assisting with retrimming an aircraft control does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Device for assisting with retrimming an aircraft control, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Device for assisting with retrimming an aircraft control will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2536452