Browse Prior Art Database

Early Determination of need to abort takeoff Disclosure Number: IPCOM000236413D
Publication Date: 2014-Apr-24
Document File: 6 page(s) / 115K

Publishing Venue

The Prior Art Database


This proposal details an onboard aircraft monitoring system capable of real-time detection of an unsafe takeoff-in-progress due to abnormally slow acceleration and/or excessive runway usage. This describes a method to provide an early alerting to the pilot if the assumptions used during takeoff planning are not correct, resulting in a takeoff e acceleration that is not sufficient for a safe takeoff.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 20% of the total text.

Page 01 of 6


During an aircraft's takeoff roll, certain indicated airspeeds are called out by the pilots as 'benchmarks' to measure progress down the runway. There are typically four speeds called out: 80 knots, V1, VR and V2. V1 is known as the "takeoff decision speed" and may be considered the most important speed to reference during the takeoff roll. Prior to reaching this speed, there is enough braking power and available runway length remaining to safely abort the takeoff if the need should arise-however; once this speed is exceeded the takeoff must be continued regardless of system failures that might occur (e.g. engine failure). Deciding to abort the takeoff after this point may likely result in a runway overrun, brake/tire system failure, or both. VR is the rotation speed, which is the speed the aircraft starts to transition into the air. The final speed for takeoff is V2 which is the speed that must be attained at liftoff and the speed to maintain if one engine is out. Together these speeds are referred to as the Vspeeds and they are used to ensure that the takeoff and initial climb over obstacles can be accomplished with appropriate safety margins.

These speeds are computed based upon many environmental factors that vary for each flight. In order for these speeds to be valid, an assumption is made that the aircraft will accelerate as expected, as well as properly utilize the specified amount of available runway. In reality, if these criteria are not met, the aircraft may not reach its decision speed until it is well past the intended location along the runway where this speed was supposed to have been achieved. If this anomaly goes undetected, the aircraft may overrun the end of the runway either in an attempt to stop, or even worse during the normal takeoff attempt. Either scenario carries with it the very real potential to seriously damage the aircraft and/or cause human fatalities.

The following is a description of the speeds that are used during takeoff. There are many other speeds that are used during the initial climb after takeoff and throughout the flight, but the speeds listed below are of primary concern for the takeoff portion of a flight.

V1 - Critical engine failure speed or decision speed. Engine failure below this speed should result in an aborted takeoff; above this speed the takeoff run should be continued. If the aircraft has an engine failure prior to reaching V1, the takeoff can be aborted and aircraft braking will stop the aircraft before the end of the runway. If an engine fails after reaching V1 the takeoff must continue as the aircraft cannot safely stop before the end of the runway. [2]

The actual speed is compared with the computed V1 speed by the pilot during the takeoff roll so the crew can respond promptly and correctly if a takeoff needs to be aborted. As part of computing the V1 speed, the avionics also computes the location where the V1 will be reached. This is used later to determine...