I watched a video today from Mentor Pilot on YouTube about the crash of Air Florida flight 90 in 1982.
I don’t think that there is a huge amount for GA to learn from it, but it did bring up an interesting aspect. It said that the captain would have expected the take off roll to last about 30 seconds, but on this occasion it actually lasted 45 seconds. Despite it taking 50% longer than expected, the captain didn’t react or take any action based on the longer take off time.
This got me thinking about rejected take offs. I think in GA they are pretty rare (at least outside training), and so maybe there is a useful conversation to be had about sharing our stories of rejected take offs.
I have two stories that I can share.
I personally have only ever rejected one take off (at least only one that I can remember). That way maybe 10 years ago. I was flying an aircraft that I knew well, from Dublin airport (EIDW). Nothing was unusual about the flight until I started my take off run. Acceleration was normal, and I was maybe 3/4 of the way up to take off speed, then the engine gave one ‘cough’.
When I say a cough, I don’t mean it sounded like it was going to cut out. It just had a quick ‘noise’ (not a bang/explosion…sorry I can’t describe it as anything better than a cough noise) and there was a very momentary lose of power. So momentary that it had recovered in the time it took me to look down at the panel. Maybe it lasted 0.5 seconds.
I pulled the throttle, and rejected the take off.
We had no access to any engineering facilities on site. I checked everything that I could think of, and couldn’t find anything wrong.
I did an extended engine power check and there was no problem to be found.
I then ran the engine at near full power for a few minutes on the ground and again didn’t find any issues.
I suspected that perhaps a small amount of dirt or water got into the fuel and was sucked through and was now clear. So I went flying. It was just planned as a local flight with nothing much in mind, so I kept pretty close to the airport just in case.
All was fine until about 20 minutes into the flight, when a small vibration developed. It was only a very slight vibration. Nothing evident from any of the gauges other than a 5kt loss in normal IAS. My passenger (another pilot) hadn’t even noticed it, it was that slight. I immediately returned to the airport and had a normal landing.
After parking up and and putting my stuff away, I had a look around the aircraft. A small puddle of oil had developed underneath. It turns out we had a bent push rod.
Over the years I’ve often thought about that decision to go flying afterwards. I know many might say that it was the wrong decision. But what was the alternative? Ask an engineer to travel (given the travel time it would have been a full day for our engineer to travel to the aircraft, inspect it and return to their base) to look at a fault that had resolved in an instant and couldn’t be reproduced? The answer would probably have been “If it’s not happening now, why don’t you fly it to me and I’ll take a look”, in which case I might as well fly it anyway.
I’m not asking anyway to second guess my decision. It’s made, and I’ve given it a lot of thought over the years, and I’m ok with the decision that I made. I only post it as an opportunity for others to mull over and think about the subject of rejected take offs.
But in many ways, that was an easy one. The engine did something obvious and required an instant reaction at the time.
Story two happened to a friend of mine. We were flying two aircraft in convoy (same trip, same times but not in formation).
We stopped overnight in the Channel Islands. On departure the next morning, my friend rejected his take off about half way through.
We had a brief conversation by phone after I landed at the destination (I’d taken off a few minutes before him and this was only to be a short flight to first clear customs into France). He explained that he didn’t believe the aircraft was accelerating like normal and he decided to reject the take off.
This was a Sunday, and we were very lucky. The airport contacted the local engineer who was willing to come to work on the Sunday to take a look at it for us. It turned out that a small plug had fallen out of one of the cylinders allowing too much air in, which meant that one of four cylinders was not producing proper power. (Maybe no power at all….I’m not sure). He sorted it out, and we were back in business.
Speaking to my friend that evening I complimented him on noticing the loss of power, even though the aircraft was still accelerating and he had loads of runway left, and he believed that he’d have no difficulty taking off. He said that aircraft was accelerating and he couldn’t be sure that it was slower than normal, but he wasn’t comfortable that he was getting full power. He had no doubt that he had sufficient runway left to take off with the acceleration that he was getting.
I thought that was a very good decision for a pilot who might have had a lot of reasons not to trust their intuition:
1. The aircraft was still accelerating
2. They weren’t sure that they weren’t getting fully power. There might have been nothing wrong.
3. They had sufficient runway left
4. They had no doubt that they could take off. The concern was that they were taking off in a suboptimal aircraft rather than they wouldn’t get into the air.
5. They were away from base with no knowledge of any engineering support available
6. It was a Sunday and realistically he couldn’t have expected any help until at least the following day
7. His friend had already departed.
He told me that it was already on his mind from the previous day. He said that he felt the aircraft was having a harder time maintaining the altitude (flying slower) in the cruise on the last flight of the previous day. He’d put it down to flying much higher than normal and the weather being much hotter than normal. But it had been on his mind overnight and that had primed him to pay extra attention to the acceleration on take off. That greatly increased his decisiveness in the moment.
Do you have any stories of a rejected take off that you’d like to share?
Or maybe even more interestingly, a take off that you didn’t reject and subsequently thought that you should have rejected it?
As these are relatively rare in GA, maybe we can learn something from sharing our stories. If nothing else, maybe reading these stories, it might refresh the thought in our minds that we should be mindful of the possible need and the option to reject a take off before we line up next time. Maybe in doing so we can help one another avoid the mistake of the captain of Air Florida flight 90.
Do you prefer full power loss? or partial power loss?
I rejected once but instructor took-over and continued the takeoff, we had a long debate afterward on what was the issue but I just did not like ASI stuck at 55kts for very long but he did not feel it was that slow, our perception was relative but we had plenty of runway, on a short runway it would have been an interesting experience 
The other ones,
- G1000 where ASI did not kick in until +40kts
- Departing on one mag on a very hot day
I still wonder what would have been the one mag ceiling of a C172 at MTOW but I believe about 4kft ?
Aside from training, I can only remember one. Taking off from Tangiers in a 172RG the airplane vibrated like it was falling apart. I knew the shimmy dampener wasn’t great on that one, but this felt like I was about to lose the nosewheel or something else. Aborted, taxied clear and checked the gear assembly carefully. All seemed well so did another takeoff run, this time holding full aft elevator to unload the nosewheel as much as possible. Worked and flew back home (to Malaga at the time). The mechanics repaired / replaced the shimmy dampener the next day.
My last rejected takeoff was at EDTF (Freiburg) a few weeks ago. We were already lined up when a helicopter, who did some exercises before parallel to the runway, asked politely if he could depart first. No factor, we agreed on it. After his departure I did apply full power. Suddenly the guy on tower advised us to hold position, although we have been accelerating at this time, because a second helicopter who has not been on the radio before entering the runway in front of us. The pilot was a real assh… because even then he was not talking at all to us about his intentions. Finally he left the runway heading turning northbound, while the other one was turning southbound before. No comments neither from the guy on the tower nor from the helicopter pilot, when we where complying about this rude behavior on the radio.
Only one so far, about 3 years ago in Berlin. Piper 28. Acceleration was normal but somehow asi didn’t reflect the speed I felt.
Stopped at what was probably already rotating speed but IAS was 40 kts
Found a small insect in the pitot tube.
Lesson learned: be extra thorough when checking the pitot tube.
Interesting post, DP.
I don’t think you had much logical choice on that “bent pushrod” case, because the practicalities of an engine doing “something funny” is a teardown of the engine! Well, you could have replaced the fuel servo. These are pretty drastic actions. I wonder how the pushrod got bent? Only a stuck valve should do that.
The only other thing one could have possibly done is to download and examine an EDM700 or similar log. I’ve had a loss of power flying Shoreham to Antwerp in Belgium, years ago. A few seconds, I thought. After landing, took the cowlings off (with the help of the friend I was meeting there) and found nothing. Flew back. Later, the EDM700 download showed absolutely nothing! It was just my imagination. Perhaps a blocked tube in the vestibular system, with the pressure buildup (it was during descent) blocking the sound for a bit and making me think the engine was not running.
I rejected a takeoff just once, when the flow transducer for the Shadin fuel totaliser failed. I check takeoff fuel flow (about 25 USG/hr) on each takeoff and saw it was zero. It could have been a major fuel leak, perhaps. Took the cowlings off, found nothing. I have, in my toolbox, a pulse generator which can be connected into the sensor cable and which fakes 25 USG/hr (details here) and connecting that immediately showed that the sensor was dead. They are designed to not block the flow even if the turbine rotation is blocked, so I did the flight (to Lausanne in Switzerland – which is about 1/2 tank so the fuel totaliser was not needed).
In most GA airfield cases, one needs to reject immediately, or one will go off the runway.
The rejected takeoff:
The takeoff(s) I should have rejected, but didn’t:
dublinpilot wrote:
It turns out we had a bent push rod.
That happened to me in 2010. We got the same kind of problems, short strange noises and very slight vibrations. Power checks did not reveal anything. We don’t know when this happened, but possible a while ago. I noticed the strange behaviour on a round trip out of ZRH. Enroute there was nothing noticable, but when power changes occurred, the engine had small stutters. After that flight, maintenance told us to ferry it to their base which I did, absolutely no adverse engine behaviour occurred due to run up and full power check before the take off run, nor during the flight.
They then found a bent pushrod.
As the engine had 2500 hrs since new at the time and an overhaul had been in the talks for a while, we decided to pull the engine at this point, also because it was unclear how that had happened. The overhaul revealed a cracked case (very minor) but otherwise the engine had been within tolerances.
Exactly what would have happened to you did happen to me: In theory we should not have flown this plane to maintenance, in practice we did, as the engine behaved “normal”. It was a 15 minute flight, but still one which I look back at with mixed feelings. Yet, according to the maintenance guy, the bending of the rod may have happened several hours ago without anyone noticing.
As for the sad case of “Palm90”, they did a lot of things wrong. First of all, they had busted the hold over time for the deicing. 2ndly, they missed putting on engine anti icing for take off, hence their EPR gauges showed way too much power. Hence, they had a contaminated wing plus way too low take off power. De-icing at the time was done at the gates so with heavy snow, it was pretty impossible to get to the runway within the hold over time of the then Type 1 fluid in use.
In the aftermath, one suggestion the captain had mentioned on the CVR before the crash became reality: The construction of de-icing pads near the runways, to save hold over time.
I’ve rejected a take-off once when airspeed failed to indicate. Turned out I’d left the pitot on during maintenance and it had melted the hose.
Most of the rejected takeoffs I have experienced have been due to a door popping open. As a standard procedure, I check MP, RPM, fuel flow, and EGT after applying full power. I also do an acceleration check and must have 70% of lift off speed at half of expected takeoff roll. Sea level roll for me is about 1000 feet, with a 70 Kts rotate speed, so I verify I have 50 Kts at the 500 ft marker.
