Between a rock and a hard place: Too slow to take off, too fast to stop.

Years ago, when the Federal Aviation Administration was cranking out training films on nearly every conceivable aviation subject, there was a frequent flow of movies between my aviation classrooms at The Ohio State University and the lending facility in Washington, DC. Most of these films were good teaching aids and some were not worth the cost of shipping them back and forth.   

One of the best FAA movies featured a fictional commercial photographer/pilot who embarked from a sea-level airport in his brand new A-36 Bonanza on an assignment to cover the American west.

 

Typical Beech A-36 Bonanza

  

That was a rather daunting project to say the least…the American west is a huge area. The situation wasn’t helped at all by the pilot's false expectation that "this baby can take me anywhere I need to go." As he ventured farther west into higher terrain he discovered his non-supercharged Bonanza was losing performance on takeoff and climb and finally, after a frightening episode at a short grass strip high in the Colorado mountains, he understood the meaning of density altitude…which of course was the subject of that FAA film.

    

When a pilot adopts the mindset that a relatively high-powered airplane will overcome all obstacles ("this baby can take me anywhere I need to go"), the stage is set for an unpleasant surprise at best, a mishap at worst. The problem is of more concern when you're flying an airplane with two reciprocating engines because a twin doesn't perform well in an engine-out situation. Like any other fixed-wing flying machine, a twin requires a certain distance to accelerate to flying speed and if that distance is longer than the runway there may be  trouble in the offing.

Case in point…a Cessna 340A pilot invited three friends to join him for a flight to Chicago for dinner; the destination airport was Meigs Field, Chicago’s downtown airport, just a short taxi ride to the Loop and its array of fine restaurants.



Meigs Field in 2001, prior to its destruction in 2003.

Was the airport convenient? Yes. Demanding? Sometimes, because Meigs’ single north-south runway was only 3900 feet long with Lake Michigan at both ends; there was a significant obstacle (the Adler Planetarium) a short walk north of the runway and a near-constant crosswind (this is Chicago, folks...The Windy City).

The event at hand took place on a balmy summer evening; when the pilot and his passengers returned to the airport the temperature was still nearly 80 degrees with a light breeze from the southeast. Meigs Field went out of business, so to speak, at 10 pm every day and the pilot had to hustle to get off the ground before the deadline.

Nonetheless, at ten o’clock sharp the 340A started its takeoff roll to the south. In the pilot’s words "as we were approaching 100 knots at about 2400 feet down the runway we lost power on the left engine; I was pulling the power down and began to apply brakes almost at the same moment the power came back on line. Airspeed had dropped into the 60s but the last time I looked we were in the 80s with both engines producing power. I had 900 feet or less of runway left and I made the decision that I was a lot more likely to make it to rotation than to stop."

According to eyewitnesses the airplane rotated sharply near the end of the runway (producing a shower of sparks when the tail skid hit the pavement), stalled, crashed into the lake and flipped on its back; three of the occupants survived and the fourth drowned.

What went wrong?        

The Cessna’s engines were sent to the manufacturer for a complete inspection and evaluation. Even though they had been submerged for almost a full day, both engines started and ran at full power…there appeared to be no reason why they would not have performed as advertised.

The pilot’s decision to continue the takeoff when he noticed an un-commanded power reduction started the accident ball rolling, so to speak. Thorough multi-engine training should prepare a pilot to react to any indication of engine problems on the runway by aborting the takeoff. But here’s the fundamental question: why couldn’t this pilot stop the airplane in the runway remaining following the power loss?

There are at least four possibilities: one, the brakes may not have been in good condition; two, the pilot probably didn’t apply maximum braking; three, the time spent trying to resolve the problem was time wasted, in terms of runway used. You’ll find the fourth possibility near the end of this post.

Worn brakes?…maybe a factor, maybe not. As for the pilot’s braking input, "maximum braking" is a subjective term that is misunderstood by most pilots. There’s not an accurate way to know when you’ve reached the maximum; all you can do is press on the pedals until you hear the tires screaming, then back off a bit.

The third possibility is more likely than the others. Simply put, an airplane must achieve a certain airspeed to leave the ground; for a Cessna 340A at or near maximum takeoff weight the magic number is 91 knots and the distance required to achieve that airspeed is easily calculated.
Should an engine fail at or before 91 knots you have no options…close the throttles and bring the airplane to a stop.

If the problem shows up after 91 knots you have a choice; abort on the runway or continue the takeoff. The runway abort is obviously the best choice; taking a known problem into the air is never a good deal, especially when you can bring the airplane to a stop and figure things out on the ground (most light twins lose at least 80 percent of their climb capability when just one engine is running; if you’d like a close look at the terrain for several miles beyond the end of the runway, try climbing at 100 feet per minute…that is scary).

Fortunately there’s an easy way to find out what your airplane can do if you should need to execute one of these options. For a lot of years pilots had to estimate the airplane's weight, hold a wetted finger up in the wind, open the throttles, release the brakes…and hope the runway would be long enough.

Not so today, because multi-engine airplanes come equipped with Pilots Operating Handbooks (POH) that contain information for calculating takeoff performance. The POH provides the distance required to reach takeoff speed, experience an engine failure and bring the airplane to a stop; this is known as "Accelerate-stop Distance."  The POH can also provide "Accelerate-go Distance," the distance required to attain takeoff speed, experience an engine failure and continue the takeoff.

In any case, the calculated distances must be compared to the runway available. If any of the three exceed the runway length, an attempted takeoff is nothing more than a bet that neither engine will fail until the airplane is at a safe altitude.

The calculation of precise takeoff distances for most general aviation airplanes will use up a lot of time because double interpolation is required but don't despair, there’s a way to skin this cat safely; simply use the next higher increment on the charts for weight, temperature, wind and altitude and you are guaranteed a safety cushion. This is a quick way to do the job and the conservative distances that result will always be greater than the actual numbers. If you wind up with takeoff performance that still won’t fit comfortably in the runway distance available, wait until the weather improves.



Typical Cessna 340A

 I crunched the numbers for the airplane in this mishap and came up with these distances:

Normal takeoff distance               Ground roll, 1794 feet

                    Accelerate-stop distance               3662 feet

                    Accelerate-go distance                  5153 feet

Given the Meigs Field runway length (3900 feet), a normal takeoff would be a no-sweat operation, the accelerate-stop distance makes it questionable, and the accelerate-go distance is out of the question.

These are not absolute values. There’s no way to tell if the 340 could have been stopped at the far end of the runway after experiencing an engine problem at 91 knots; brake condition, pilot braking input, pilot reaction time etc. cloud the picture considerably. But had the pilot calculated takeoff performance prior to releasing the brakes and was ready to execute the emergency procedure at the first sign of trouble the outcome may have been remarkably different.

What about the fourth possibility?

I left my comments about the fourth possibility until this point for a good reason…it goes so much against the grain of pilot training and common sense it’s hard to believe a pilot would try it. Nevertheless, the NTSB investigator’s interview included this statement: "The pilot used 32 inches of manifold pressure for takeoff [the POH calls for 40 inches, if memory serves]. He was told you don’t need to use full power, it only puts more wear and tear on the engines."

Hasn’t that old wives’ tale been put to rest long since? Even if there might be a small wear-and-tear benefit in a reduced-power takeoff, a 3900-foot runway is not the place to use it.

I need to commend this pilot in one area. NTSB reports include a section for the purpose of gaining additional information from those directly involved in a mishap. One of the blank areas is titled "Operator/Owner Safety Recommendations" in which the Cessna 340 pilot wrote "Do not land on runways that are not long enough to allow a start and stop procedure if taken fully to rotation speed and then back to zero. We did not have enough runway to stop by the time we realized we had a problem." Duh. Unfortunately, the pilot’s choice to use a reduced power setting for takeoff made a successful abort impossible.                   

Bottom line: There is no situation (except a bona fide emergency) that would justify a partial-power takeoff. Always use full power…it's not going to hurt the engines. And that’s why the accident airplane used  2400 feet of runway to achieve takeoff speed instead of the normal 1800 feet,  putting the pilot between a rock (too slow to fly) and a hard place (too fast to stop).