I'm sorry, I know anything is possible under the right mix of circumstances but I am still at a loss to understand how this actually happened without being detected until it was very nearly too late in the take off.
I can assure readers from personal experience that the detection of slower than expected acceleration is difficult particularly at night. It is only until almost at the end of the runway when you realise something is wrong. Rather like overtaking a vehicle going 10 kms slower than you on a freeway. While a long way behind the vehicle the rate of closure seems very slow then as you draw alongside you are now conscious of almost speeding past the vehicle.
Nearly 30 years ago, an Air Nauru 737-200 lined up for a night take off from the 5600 ft length runway on Nauru. No overun area - just boulders and a 20 feet drop into the water. Max bleeds off take off due runway performance limited. Planned EPR 2.18 which is full power.
80 knot call made by the captain who was PNF. Passing 110 knots the 737 would normally be passing abeam the control tower which is close to the runway. Very black hole take off over water. It was only when about five runway lights were left to go when the penny dropped that the 737 was well below V1 and never going to get airborne in the remaining runway length. An abort was now out of the question so the captain took control and fire-walled both thrust levers against the mechanical stops at the same time hauling back on the control wheel. The jet blast lifted concrete from the perimeter road back along the runway.
Later investigation revealed that at no point during the take off roll did the engines develop full thrust - although both EPR gauges indicated full 2.18 EPR thrust was achieved. In fact, it was calculated later the EPR gauges had over-read by nearly ten percent which resulted in significantly reduced thrust. The trouble was caused by the engines inlet sensors called Pt2 tubes which were later found to be blocked by a combination of phosphate dust and insects because engine covers were not in place overnight.
Close inspection of the N1 compressor gauges on the instrument panel would have revealed the lower than expected N1 readings during take off but for various reasons none of the three crew members in the cockpit that night double checked the N1 readings against the indicated EPR digital read-outs.
It was an almost identical situation to that of the 737-200 that crashed into the Washington Potomac River due to iced up Pt2 sensors on both engines that resulted in faulty EPR readings. In that case the F/O as PF was aware that `something was not quite right`during the take off roll but was unable to pin-point the problem which was lack of expected acceleration.
The captain failed to fire-wall the engines and the 737 clipped a bridge and crashed into the river killing most on board. Fortunately the captain of the Air Nauru aircraft did fire-wall the engines at the last few seconds of the take off roll and that saved the day.
Putting aside the blame-game that later ensued where the Air Nauru captain was hung out to dry by management, it was clear to this writer (I was in the jump seat) that the slower than normal full power acceleration during the take off roll at Nauru was never enough to alert the crew to an impending serious accident because the sensation was so subtle. The dark night scene didn't help. It was only in the last few seconds of the take off roll that a positive picture of the true situation became apparent. All three crew members were fooled.
The same take off thrust actually achieved that night during the majority of the take off roll at Nauru, was identical to the reduced thrust settings used on longer runways such as Guam or Hong Kong when calculated by the Assumed Temperature method. That was around 2.10 EPR. The difference of throttle angle between 2.18 EPR and 2.10 EPR is quite small. The clue was in the readings of the N1 compressor where the instrument dial is quite small and N1 needle readings small scale and hard to see at night.
Ironically if one only engine Pt2 sensor had been blocked at the time of the incident, the subsequent split throttle position needed to set equal EPR needle readings would have alerted the crew early enough in the initial take off roll to safely reject the take off. In fact this had happened to another crew on Nauru a few weeks earlier. It was an unfortunate quirk of fate that both engine Pt2 sensors suffered similar blockages leaving both EPR gauges giving identical readings as expected during a normal take off.