Dusting off the FAA takeoff safety training aid
I teach Aircraft Performance for commercial pilots (ATPL) and the question that ALWAYS comes when we talk about V1 is:
- What if something happens after V1 and the runway is long enough to stop on?
The simple answer is: You fly.
The catch is: What if you think the aircraft can not fly? How do you know if you are right?
Thanks to a report by the Dutch Aerospace laboratory NLR this matter has new fuel in the form of statistical data and a long forgotten safety program.
High speed abort: faster than 80 knots
After call “80” at 80 knots, the takeoff is only aborted for serious events such as engine failure, engine fire, directional controls or an obstructed runway. Some operators choose 70 or even 100 knots but most use 80. This is also because most modern airplanes have a flight phase inhibit for certain warnings at that speed up to 1500 feet AGL.
V1 is usually higher than 80 kts. A typical value for a Challenger 350 is between 119 and 130 kts. Then there is also reaction time:
With a typical acceleration of 3 to 6 knots per second, just 3 seconds for assessing the situation and decision-making, will add 9 to 18 knots to the speed. If the aircraft is close to V1, it now most likely has exceeded it.NLR-TP-2010-177
For this report a dataset of 135 high speed aborts was analyzed. There are some interesting numbers in there:
In more than 80% of the high speed aborts, the decision was made after V1
- In 90% of these cases the aircraft could not be stopped on the runway.
- In about half of those cases, the decision to abort was correct or unknown
Only 20 to 25% of all rejected takeoffs are caused by engine failure.
The other 75% by something else.
The Takeoff Safety Training Aid
An old FAA training tool exists, called “The Takeoff Safety Training Aid.” The program consists of a detailed article with the title “Pilot Guide to Takeoff Safety” and a movie: “Rejected Takeoff and the Go/No Go Decision”
The movie looks like a VHS-style movie from the previous century (because it is) and can be found on Youtube:
The full description of the Takeoff Safety Training Aid can it be found under this link.
Has the question been solved: What if there is enough runway after V1?
Well, how do you know if it is enough? And also, how do you know if the failure prohibits the aircraft from flying?
There are plenty of cases where the late decision ended badly:
Runway Overrun During Rejected Takeoff in Bedford, MA 5/31/14
Bizarre stuff, good material for lessons on the importance of sop’s.
Ilyushin IL-18 Aborted take off
Runway overrun after rejected take-off, MD-88, Groningen Airport Eelde
On the runway checks were performed. FDR data indicated a stabilizer position change from 6.8 to 7.2 degrees aircraft nose up (ANU). Thereafter the crew initiated a static engine spin-up. Again the stabilizer warning sounded. The crew released the brakes and started the take-off roll. From the CVR it is derived that during the entire take-off roll the warning sounded continuously.https://https://www.onderzoeksraad.nl/en/page/750/runway-overrun-after-rejected-take-off-md-88-groningen-airport-eelde
When attempting to rotate the captain experienced a heavy elevator control force. The captain stated that he needed much more than normal back pressure on his control column to lift the nose. He felt ”it was impossible to make the take-off”, and as the nose did not rise he decided to reject the take-off. Post accident analysis revealed that the rejection was initiated at 128 knots.
I guess it remains a problem. Apart from some of the strange decisions above, the only time where it is actually very clear that you can and must stop after V1 is in the sim on a 4 km runway where at Vr you feel that the elevator has “mysteriously” become jammed so you stop on the remaining 3 km of runway….
It isn’t always that obvious:
- UPS MD11 at Seoul on Jun 6th 2016, rejected takeoff, runway overrun results in nose gear collapse
- Air Berlin B738 at Dortmund on Jan 3rd 2010, rejected takeoff results in runway overrun
But sometimes regrettably also very catastrophic
Learjet 60 runway overrun, Columbia Metropolitan Airport, SC (CAE) Friday 19 September 2008
According to the report it is a about a 50/50 choice:
Many high speed rejected takeoffs (44%) should not have been conducted. This number is only slightly less than before the introduction of the training aid (51%); Pilots have difficulties in recognising “unsafe to fly” conditions.