Detecting that a rotorcraft is approaching a vortex domain, and signaling that detection

Patent metadata

Field	Value
Publication number	US-10358232-B2
Application number	US-201715633925-A
Country	US
Kind code	B2
Filing date	Jun 27, 2017
Priority date	Jun 28, 2016
Publication date	Jul 23, 2019
Grant date	Jul 23, 2019

Abstract

A method and a device for detecting that a rotorcraft is approaching a vortex domain. After previously determining a limit advance speed threshold and a limit vertical speed threshold defining a limit for said rotorcraft entering into a vortex domain, a predictive advance speed and a predictive vertical speed for said rotorcraft are calculated, said predictive vertical speed being calculated differently depending on the value of said instantaneous advance speed. Thereafter, said predictive advance speed and said predictive vertical speed are compared with said thresholds, which may be thresholds with hysteresis, in order to determine whether said rotorcraft is approaching a vortex domain, and if so to signal this situation to a pilot of said rotorcraft.

First claim

What is claimed is:

1. A method of detecting that a rotorcraft is approaching a vortex domain, and of signaling that detection, the rotorcraft forming part of a rotorcraft family and having a main rotor with blades, wherein the method comprises the following steps:
a) a preliminary step of determining a limit advance speed threshold and a limit vertical speed threshold defining a limit for entering into a vortex domain for the family of rotorcraft;
b) a calculation step of calculating in real time a predictive advance speed and a predictive vertical speed of the rotorcraft during a flight of the rotorcraft;
the predictive advance speed being calculated as a function of an instantaneous advance speed and of an instantaneous advance acceleration of the rotorcraft over a prediction time interval Δt characterizing the prediction time of the predictive advance speed and of the predictive vertical speed; and
the predictive vertical speed being calculated on the basis of the instantaneous advance speed,
when the instantaneous advance speed is greater than an upper limit speed, the predictive vertical speed being calculated as a function of the instantaneous vertical speed of the rotorcraft, of the energy balance of the rotorcraft, and of the power variation needed by the main rotor for level flight over the prediction time interval; and
when the instantaneous advance speed is less than a lower limit speed, the predictive vertical speed being calculated as a function of the instantaneous vertical speed and of an instantaneous vertical acceleration of the rotorcraft;

c) a step of triggering an alarm that a rotorcraft is approaching a vortex domain, the predictive advance speed and the predictive vertical speed being compared respectively with the limit advance speed threshold and with the limit vertical speed threshold, the alarm being triggered when firstly the predictive advance speed has reached the limit advance speed threshold, and secondly the predictive vertical speed has reached the limit vertical speed threshold; and
d) a step of signaling the alarm to a pilot of the rotorcraft as a result of the triggering of the alarm.

2. A method according to claim 1 , wherein when the instantaneous advance speed is less than or equal to the upper limit speed and greater than or equal to the lower limit speed, the predictive vertical speed is an interpolation between the above two situations, i.e. when the instantaneous advance speed is greater than the upper limit speed or when the instantaneous advance speed is less than the lower limit speed.

3. A method according to claim 1 , wherein when the instantaneous advance speed is less than or equal to the upper limit speed and greater than or equal to the lower limit speed, the predictive vertical speed is calculated using logic with hysteresis between the two above situations, i.e. that when the instantaneous advance speed decreases from the upper limit speed and remains greater than or equal to the lower limit speed, the predictive vertical speed is calculated using the first situation, i.e. as a function of the instantaneous vertical speed, of the energy balance of the rotorcraft, and of the variation in the power needed by the main rotor for level flight over the prediction time interval, and when the instantaneous advance speed increases from the lower limit speed and remains less than or equal to the upper limit speed, the predictive vertical speed is calculated using the second situation, i.e. as a function of the instantaneous vertical speed and of the instantaneous vertical acceleration of the rotorcraft.

4. A method according to claim 1 , wherein the calculation step comprises substeps:
b1) a substep of determining the instantaneous advance speed and the instantaneous vertical speed of the rotorcraft;
b2) a first calculation substep of calculating the predictive advance speed using a first relationship:

V
AP

=

V
A

+

Δ
⁢

⁢

t
·

dV
A

dt

where t and Δt designate respectively time and the prediction time interval, being an instantaneous advance acceleration of the rotorcraft;
b3) a second calculation substep of calculating the predictive vertical speed on the basis of the instantaneous forward speed,
when the instantaneous advance speed is greater than the upper limit speed, the predictive vertical speed is calculated using a second relationship:

V
ZP

=

V
Z

+

A
·



V
A

·

dV
A

dt



+

B
·

(

V
Z

+
k

)

·

V
AP

-

V
A

2
·

V
Y

-

V
AP

where k is a constant characteristic of the rotorcraft family of the rotorcraft, A is a first weighting coefficient, B is a second weighting coefficient, and V y is a predetermined minimum power speed of the family of the rotorcraft, the expression:

B
·

(

V
Z

+
k

)

·

V
AP

-

V
A

Assignees

• Airbus Helicopters

Inventors

• Certain Nicolas
• Pignier Lionel

Classifications

• B64D45/00 Primary

  Aircraft indicators or protectors not otherwise provided for · CPC title

• B64C27/04

  Helicopters · CPC title

• B64C27/006 Primary

  Safety devices · CPC title