Takeoff Safety

Statistics

Runway safety related accidents and incidents are aviation’s number one safety related risk category, with 59 reported accidents in 2016, of which more than half were due to runway excursions. The infrequency of RTO events may lead to complacency about maintaining sharp decision making skills and procedural effectiveness. In spite of the equipment reliability, every pilot must be prepared to make the correct Go/No Go decision on every takeoff-just in case.

By contrast, the large number of takeoffs that are successfully continued with indications of airplane system problems such as caution lights that illuminate at high speed or tires that fail near V1, are rarely ever reported outside the airline’s own information system.

Approximately one-fifth were initiated because of engine failures or engine indication warnings. The remaining seventy nine percent were initiated for a variety of reasons which included tire failures, procedural error, malfunction indication or lights, noises and vibrations, directional control difficulties and unbalanced loading situations where the airplane failed to rotate.

Approximately 52% of the events, the airplane was capable of continuing the takeoff and either landing at the departure airport or diverting to an alternate. In other words, the decision to reject the takeoff appears to have been “improper.”

What is the proper operational meaning of the key parameter “V1 speed” with regard to the Go/No Go criteria? The pilot’s initiation of the first action to stop the airplane during the accelerate-stop tests.

Transition Times

An average of the recorded data from at least six of these RTOs is then used to determine the “demonstrated” transition times. The total flight test “demonstrated” transition time, initial brake application to speed-brakes up, is typically one second or less. However this is not the total transition time used to establish the certified accelerate-stop distances. The certification regulations require that additional time delays, sometimes referred to as “pads”, be included in the calculation of certified takeoff distances.

Although the line pilot must be prepared for an RTO during every takeoff, it is fairly likely that the event or failure prompting the Go/No Go decision will be much less clear-cut than an outright engine failure. It may therefore be unrealistic to expect the average line pilot to perform the transition in as little as one second in an operational environment. Human factors literature describes the line pilot’s job as a “complex task” since the pilot does not know when an RTO will occur. In consideration of this “complex task”, the flight test transition times are increased to calculate the certified accelerate-stop distances specified in the AFM. These additional time increments are not intended to allow extra time for making the “Go/No Go” decision after passing V1. Their purpose is to allow sufficient time (and distance) for “the average pilot” to transition from the takeoff mode to the stopping mode.

While a great deal of attention is focused on the engine failure case, it is important to keep in mind, that in over three quarters of all RTO accident cases, full takeoff power was available. It is likely that each crew member has had a good deal of practice in engine inoperative takeoffs in prior simulator or airplane training. However, it may have been done at relatively light training weights.

The Flap setting

While we have to take in consideration various factors (rwy condition, weather, rwy size, weight, flap setting, etc.), at the end we are choosing to mitigate more the Go decision or No-Go decision risks when we choose a flap setting. Taking into account that the aviation industry has improved significantly when it comes to engine failure, and that from incidents from the last 20 years, only 1/4 where caused by ENG degraded performance, I strongly believe that using a higher flap setting when obstacle is not a factor. Consequently this will increase my RTO margins.

ICAO has RWY Excursion under the top safety issues.

In the example above, if there are no other constraints such as obstacles or critical noise abatement procedures that would prevent the selection of a greater flap setting, the crew could give themselves 1000 feet of extra stopping distance in case an RTO was required on this takeoff. At the end you are choosing your battles, so a good question to ask yourself: What kind of failure is more common nowadays (probability)? What are the consequences (Severity)?

The V1 call

Basic operating procedures call for the pilot flying the airplane to include airspeed in his instrument scan during the takeoff ground roll. Hence he is always aware of the approximate speed. The pilot not flying monitors airspeed in more detail and calls out “Vee One” as a confirmation of reaching this critical point in the acceleration.?

The pilot flying cannot react properly to V1 unless the V1 call is made in a timely, crisp, and audible manner. One method of accomplishing this by a major U.S. carrier is their adoption of a policy of “completing the V1 callout by the time the airplane reaches V1.” This is an excellent example of the way airlines are implementing procedures to improve RTO safety. It is a good procedure and it should preclude a situation where the “No Go” decision is inadvertently made after V1. However, the success of such a policy in reducing RTOs after V1, without unduly compromising the continued takeoff safety margins, hinges on the line pilot’s understanding of the specific airplane model’s performance limitations and capabilities.

Another proposal for calling V1 is to use a call such as “Approaching V1” with the V1 portion occurring as the airspeed reaches V1. Either of these proposals accomplish the task of advising the flying pilot that the airplane is close to the speed where an RTO for all but the most serious failures is not recommended.

Crew preparedness

Important crew factors directly related to eliminating RTO overrun accidents and incidents are:

• Brief those physical conditions which might affect an RTO that are unique to each specific takeoff.
• Both pilots must be sure to position the seat and rudder pedals so that maximum brake pressure can be applied.
• Both pilots should maintain situational awareness of the proximity to V1.
• Use standard callouts during the takeoff.
• Transition quickly to stopping configuration.
• Don’t change your mind! If you have begun an RTO, stop. If you have reached V1, go, unless the pilot has reason to conclude that the airplane is unsafe or unable to fly.
• Use maximum effort brake application.
• Assure deployment of speed-brakes.
• Use maximum reverse thrust allowable.

The Stop Callout

In lighter aircrafts like business jets, the time from 80 kt to V1 is pretty low, maybe just a few seconds. The recommended word for an RTO is "STOP". PF and PNF should always rely on each other as professionals and doubting or trying to figure out what is going on before a decision would increase the chance of an incident.

Briefing

Poor briefing has been a factor in many incidents. Many just make the briefing like reading a book in auto mode, the PNF will probably be lost during a briefing like this. There are many types of briefings that are objective, concise, clear and involves the PNF into the briefing (I plan to do an article on that), like for example asking the PNF at the beginning what Hazards we have for this takeoff, after those hazards are pointed out you can brief the mitigations for that and continue the safety briefing.

References:

• AC 120-62
• IATA
• ICAO Safety Report 2019
• Flightsafety Foundation
• Skybrary