Automatic detection of rotary wing aircraft take-off and landing

Abstract

An apparatus to determine take-off and landing times for a Rotary wing aircraft by the measurement and analysis of the atmospheric pressure changes around or within the aircraft. This may be done acco

Description

This invention is a system for automatically detecting take-off and landing of a General Aviation helicopter. Accurate recording of times at which a helicopter takes-off and lands is essential to helicopter operations for engineering and commercial purposes. Traditionally, the times of take-off and landing are recorded by the pilot, with attendant inaccuracy, or relied on equipment that is connected to the aircraft control system. The latter requires the system to be approved for the purpose, resulting in high capital and operating costs. Due to its ability to hover, detecting the point at which a helicopter takes-off and lands without directly monitoring the aircraft controls or by weight sensors is complicated by the fact that the vertical motion involved is variable and is not limited to take-off and landing. At take-off it is standard practice for the helicopter to hover-taxi a few feet above the ground away from the landing pad before climbing away. Similarly, when landing, the initial descent to a few feet above the ground is typically followed by a hover-taxi to the landing pad. In these cases, the initial lift-off from the ground and final descent to the ground will be very small vertical movements resulting in changes in atmospheric pressure which are too small to be reliably detected within the continuous minor changes (noise) in ambient atmospheric pressure. Because of this, an approach of monitoring atmospheric pressure to detect the decrease in pressure as the helicopter rises from the ground at take-off and the increase in pressure as it descends to the ground when landing is not practicable. To overcome these problems, the present invention proposes a take-off and landing detection system that detects take-off and landing by monitoring the changes to atmospheric pressure within the aircraft resulting from the increase in pressure that is generated by the downthrust from the rotors when the helicopter is close to the ground, known as ground effect. Take-off and landing are unique because they are carried out in contact with the ground and very close to it. At take-off, when rotors are adjusted to produce lift, ground effect causes atmospheric pressure around and within the helicopter to increase slightly above ambient atmospheric pressure before decreasing again as the helicopter lifts away from the ground. At landing, the atmospheric pressure around and within the helicopter will increase as the helicopter descends onto the ground, before decreasing as the rotors are adjusted to remove downward thrust and settle the aircraft on the ground. The invention will now be described solely by way of example and with reference to the accompanying drawing Figure 1 in which: Figure 1 shows a flow chart of the sequence of events that enable the invention to determine take-off and landing. The atmospheric pressure change that is used to determine a potential take-off or landing, O.lmB in the example, and the duration over which the pressure change has to be maintained to confirm the take-off or landing, 2 seconds in the example, may be adjusted to optimise performance for a given helicopter type. As detailed in the upper section (red) of Figure 1, upon switch-on of the aircraft electrical power, atmospheric pressure readings commence and are taken approximately every second until a pressure increase of greater than or equal to O.lmB is detected. A potential take-off having been identified, the time of the reading is noted and an atmospheric pressure reading is taken after a further 2 seconds. • If the reading is still greater than or equal O.lmB, the aircraft is considered airborne and the noted potential take-off time is recorded as take-off time. Atmospheric pressure readings continue to be taken throughout the flight. • If the second reading indicates the increase in pressure has fallen below O.lmB, then no take-off time is recorded and atmospheric pressure readings and analysis continue. The lower section (green) of Figure 1 shows the process for determining landing. During flight, atmospheric pressure readings are taken approximately every second. When a reading is taken indicating a decrease in pressure greater than or equal to O.lmB, a 2 second interval is allowed to elapse before another reading is taken. If a decrease of O.lmB or greater is still indicated, then touch down may have occurred and the time of the second reading is noted as a potential landing time. • If the aircraft power is switched off before a further increase in atmospheric pressure is detected, then landing is confirmed and the noted potential landing time is recorded as landing time. Atmospheric pressure readings cease and the Take-off and Landing times are incorporated in a flight message that is uploaded to a processing and distribution hub via the mobile telephone network. • If an increase in atmospheric pressure is detected before aircraft power is switched off the helicopter may still be flying, so no landing time is recorded at this time and atmospheric pressure readings continue every second.

Claims

1. An apparatus to determine the Take-off and Landing times for a rotary wing aircraft solely by the measurement and analysis of the atmospheric pressure changes around or within the aircraft produced by the downthrust from the aircraft rotors when the aircraft is on the ground.

2. An apparatus to determine the Take-off and Landing times for a rotary wing aircraft according to Claim 1 incorporating means to analyse the change of atmospheric pressure around or within the rotary wing aircraft according to specified parameters.

3. An apparatus to determine the Take-off and Landing times for a rotary wing aircraft according to Claim 1 incorporating means to identify the first rise in pressure around or within the rotary wing aircraft conforming to the specified parameters following electrical power being applied to the device.

4. An apparatus to determine the Take-off and Landing times for a rotary wing aircraft according to Claim 1 incorporating means to identify the last fall in pressure around or within the rotary wing aircraft conforming to the specified parameters before electrical power is removed from the device.

5. An apparatus to determine the Take-off and Landing times for a rotary wing aircraft according to Claim 1 incorporating means to record the real time at which first rise and last fall in pressure in Claims 3 and 4 above occur.

6. An apparatus to determine the Take-off and Landing times for a rotary wing aircraft according to Claim 1 incorporating means to tailor the specified parameters of the analysis in 2 above to optimise the analysis for different rotary wing aircraft designs.