Lidle's Box: an Cirrus SR-20 turn rate story.
Over Coffee this morning the usual suspects from the Buttonville flying club kicked around the idea that the tragic accident involving a Cirrus in New York City was caused by a stall out in a steep turn. As I fly C-GOPX, a Cirrus that is the same model and year as the plane involved I was asked to speculate as to if this was a possibility.
I can not say for certain what might have happened to Cory Lidle, who played for the Toronto Blue Jays in 2003 and was currently pitching for the New York Yankees, and Tyler Stanger, his 26-year-old California flight instructor. But given the absurd speculation by others (CTV's Washington Bureau Chief Tom Clark) that they ran out of fuel, I think it is appropriate to say something.
First they did not run out of fuel. They were airborne for only a short period of time and there are fuel warning lights on the Cirrus so the chances of them running out of fuel is remote to the point were I would rule it out. If they lost engine power, all options would involve a forward looking glide, not a steep turn.
I would like to suggest some facts, based on my own experience, and a straight forward experiment that I tried while flying GOPX today. Hopefully it can shed some light on the tragedy.
1) The radar evidence on the Cirrus's flight path does indicate that it was in a steep turn at a slow airspeed.
2) The east river is about 2000 feet wide at the point were Cory Lidle and his flight instructor tried to turn around. Radar shows them starting a turn over the river, see the radar plot here: http://www.youtube.com/watch?v=AcHCCjKZBEc&eurl =
3) A standard 30-degree bank angle at a slow 100kts ( the slower the speed the less room you need to turn) would give a turn diameter of more than 3000 feet. A steeper (especially for such low time pilot) 45 degree turn still doesn't do it.
4) The last recorded ground speed given by Radar was 112 miles an hour ( about 100 kts), which is slow for a Cirrus SR-20 (normal cruise is 145- 155 kts).
5) He was flying between 700 and 900 feet before the accident, under the airspace cap of 1100 feet.
6) At this low altitude gusting mechanical turbulence from the surrounding buildings presents a complicating factor. The ceiling was 1500 ft in drizzle, exact winds in the area are unknown.
7) I calculated that to make the turn would have required an immediate 60 degree turn at 100 kts.
8) According to my Pilot operators handbook for the SR-20, with 0 dgr flaps, in a 60drg turn, the stall speed of a fully loaded cirrus with forward center of gravity (two pilots, full fuel, empty back seat) is 95 kts calibrated airspeed. This is the highest rate of turn listed in the POH.
9) Any pilot rolling into this turn, with a vertical wall in front of him will have a tendency to tighten the turn. By my calculations, about 70 drgs at 100 kts he would have been in a stall. A slight wind gust or bit of mechanical turbulence is all it would have taken to make in an unrecoverable mess.
Today I took off from Buttonville and tried to validate this with an experiment.
At 9500 feet near the simcoe VOR (YSO) I tried a 60 degree turn at 100 knots with no flaps. I then tightened this turn, to around 70 degrees, Even lightly loaded I could feel the stall coming on.
Based on this information, here is my best guess as to what happened:
Cory Lidle and his instructor was in every pilots worst nightmare, the "box canyon." they attempted to do a steep turn to get out of the box and in the process stalled into the "canyon" wall, which, due to the city landscape, happened to be a high rise.
The Cirrus is a great plane for going straight and level at an impressive speed. But like many of the newer "plastic planes" its virtues become liabilities when trying to fly low and slow. It is not an acrobatic plane or even a spin rated one. And it is not the forgiving old Cessna that Cory, and even his instructor gained most of their flight experience in. The turn they attempted would have been difficult, maybe even impossible in a Cirrus SR20, without putting down the flaps before starting the turn or breaking the flight restrictions imposed on them .
In my mind the real cause of the accident was the flight restrictions and rules that created the box canyon in the first place, and the low time pilot that didn't stay in front of the aircraft he was flying. Once he was in the turn he still had some outs, but all would have required "breaking airspace rules", he decided to stay inside the box and paid the price.
Next time some hot air politician uses this tragedy to sound off about adding additional flight restrictions to Torontos Airspace for the sake of "safety", please remind him that it was similar restrictions that created the artificial box canyon that kill Mr. Lidle in the first place.
- Mark
I can not say for certain what might have happened to Cory Lidle, who played for the Toronto Blue Jays in 2003 and was currently pitching for the New York Yankees, and Tyler Stanger, his 26-year-old California flight instructor. But given the absurd speculation by others (CTV's Washington Bureau Chief Tom Clark) that they ran out of fuel, I think it is appropriate to say something.
First they did not run out of fuel. They were airborne for only a short period of time and there are fuel warning lights on the Cirrus so the chances of them running out of fuel is remote to the point were I would rule it out. If they lost engine power, all options would involve a forward looking glide, not a steep turn.
I would like to suggest some facts, based on my own experience, and a straight forward experiment that I tried while flying GOPX today. Hopefully it can shed some light on the tragedy.
1) The radar evidence on the Cirrus's flight path does indicate that it was in a steep turn at a slow airspeed.
2) The east river is about 2000 feet wide at the point were Cory Lidle and his flight instructor tried to turn around. Radar shows them starting a turn over the river, see the radar plot here: http://www.youtube.com/watch?v=AcHCCjKZBEc&eurl =
3) A standard 30-degree bank angle at a slow 100kts ( the slower the speed the less room you need to turn) would give a turn diameter of more than 3000 feet. A steeper (especially for such low time pilot) 45 degree turn still doesn't do it.
4) The last recorded ground speed given by Radar was 112 miles an hour ( about 100 kts), which is slow for a Cirrus SR-20 (normal cruise is 145- 155 kts).
5) He was flying between 700 and 900 feet before the accident, under the airspace cap of 1100 feet.
6) At this low altitude gusting mechanical turbulence from the surrounding buildings presents a complicating factor. The ceiling was 1500 ft in drizzle, exact winds in the area are unknown.
7) I calculated that to make the turn would have required an immediate 60 degree turn at 100 kts.
8) According to my Pilot operators handbook for the SR-20, with 0 dgr flaps, in a 60drg turn, the stall speed of a fully loaded cirrus with forward center of gravity (two pilots, full fuel, empty back seat) is 95 kts calibrated airspeed. This is the highest rate of turn listed in the POH.
9) Any pilot rolling into this turn, with a vertical wall in front of him will have a tendency to tighten the turn. By my calculations, about 70 drgs at 100 kts he would have been in a stall. A slight wind gust or bit of mechanical turbulence is all it would have taken to make in an unrecoverable mess.
Today I took off from Buttonville and tried to validate this with an experiment.
At 9500 feet near the simcoe VOR (YSO) I tried a 60 degree turn at 100 knots with no flaps. I then tightened this turn, to around 70 degrees, Even lightly loaded I could feel the stall coming on.
Based on this information, here is my best guess as to what happened:
Cory Lidle and his instructor was in every pilots worst nightmare, the "box canyon." they attempted to do a steep turn to get out of the box and in the process stalled into the "canyon" wall, which, due to the city landscape, happened to be a high rise.
The Cirrus is a great plane for going straight and level at an impressive speed. But like many of the newer "plastic planes" its virtues become liabilities when trying to fly low and slow. It is not an acrobatic plane or even a spin rated one. And it is not the forgiving old Cessna that Cory, and even his instructor gained most of their flight experience in. The turn they attempted would have been difficult, maybe even impossible in a Cirrus SR20, without putting down the flaps before starting the turn or breaking the flight restrictions imposed on them .
In my mind the real cause of the accident was the flight restrictions and rules that created the box canyon in the first place, and the low time pilot that didn't stay in front of the aircraft he was flying. Once he was in the turn he still had some outs, but all would have required "breaking airspace rules", he decided to stay inside the box and paid the price.
Next time some hot air politician uses this tragedy to sound off about adding additional flight restrictions to Torontos Airspace for the sake of "safety", please remind him that it was similar restrictions that created the artificial box canyon that kill Mr. Lidle in the first place.
- Mark
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