Density Altitude and the Sudden Stop.

August 15, 2012 by Bruce Landsberg
crash cam Stinson 108

Stinson 108 that crashed not long after takeoff in Idaho

Rip Van Winkle would have had a hard time sleeping through the media blitz last week that centered on “crash cam” footage of a Stinson 108 that crashed not long after takeoff in Idaho this June. Major media outlets picked it up including CNN Piers Morgan’s interview of one of the passengers who survived without injury.

Three things stood out:

1. The pilot badly overestimated the ability of a 165-horsepower aircraft to take off and climb out at an estimated density altitude of 8,800’ msl with four adult males on board.

2. The lead up to the accident was subtle if you didn’t know what was happening. Everything moved in slow motion right up to impact. Gradually rising terrain combined with a slight downdraft, according to the pilot, shows what happens when an aircraft comes to a sudden stop in the trees. That isn’t subtle.

3. On CNN, at least, Morgan was quite restrained and didn’t make any wild statements regarding the overall safety of GA. But these types of incidents do nothing to enhance the image of GA among the non-flying public. The crash cam reinforces the bad experience.

Comments by pilots posted on the video site dispel the myth that the system or the aircraft was in any way to blame. The close-ups of the badly injured pilot were gratuitous. But it makes the case for harnesses and airbags that should be retrofitted to older aircraft and likely would have prevented most of the pilot’s injuries. The FAA has largely resolved the safety retrofit impediments, so the perfect installation isn’t the enemy of the good.

The first upgrade that I installed to a 1965 Mooney I used to fly was shoulder harnesses. The value of head and face seemed more important than some of the other goodies that I might have rationalized to install first. Aircraft without front seat shoulder harnesses make me nervous.

Density altitude is an abstract concept until it is demonstrated. Take off and climb at a 50 percent power setting (because that’s about how much power you’ll have for real) from a long runway. You will be amazed at how long it takes to get airborne and how slooooowly the machine climbs. You won’t forget how even a powerful sea-level engine is reduced to wimpiness.

The Air Safety Institute has several resources to help pilots: the Mountain Flying online course, the Density Altitude safety quiz, the Decision Making for Pilots safety advisor, and the Do the Right Thing online course.

 

 

 

Bruce Landsberg
Senior Safety Advisor, Air Safety Institute

ASI Online Safety Courses  |  ASI Safety Quiz  |  Support the AOPA Foundation

15 Responses to “Density Altitude and the Sudden Stop.”

  1. Tony O'Brien Says:

    The facts are simple, we need to do the right thing as PIC. Weight and Balance will solve this issue each time, yet most of us fail to comply with aviation law, why? I would throw out there we are lazy pilots, we take aviation for granted and become bullet proof in our minds. Crashes can’t happen to me.

    This accident was clearly preventable, the PIC failed to exercise is required rights and almost caused the death of 4 people.

    When we learn and wake up these stories will stop.

  2. Craig Marckwardt Says:

    My second flight as a student was out of 5T6 (Santa Teresa NM, 4110 MSL) on a hot day (90 degrees Farenheit). My first flight was from KGPM (Grand Priairie, TX…506 MSL) at 78 degrees Farenheit. Both planes were comparable Cessna 172 SP’s with me, a CFI and my grandson aboard. I learned early that the amount of runway and rate of climb with a 6000 foot difference in density altitude are jarringly different. That lesson will stick with me.

    I would suggest that every pilot in training could benefit from the same experience. If nothing else, do your cross country in hot weather, and fly either uphill or down. Back-to-back comparisons are always more profound.

    And, never guess about performance. The reason the POH exists is to keep me from doing something thoroughly stupid with my grandkids aboard. That is focus!

  3. Bob DIlk Says:

    I think this flight is partly a result of our general training. If you do the take-off calculation even at this high DA the data shows the runway was long enough. The real issue was the inability of the aircraft to climb after take-off.

    Several pilots I know will confuss to getting into marginal climb stituations after take-off, but they lucked out. How many pilots calculate the climb available?

    The second issue was the pilots failure to recognize the trouble he was in after takeoff. He flew over serveral good landing spots before running out luck and hitting the trees.

    To his credit the pilot flew the aircraft all the way to the crash site. By not stalling the aircraft he was able to minimize the injury to the occupants.

  4. Lee Taylor Says:

    I teach one thing different about takeoffs on each and every flight.
    Last thing before throttle forward, a short stop on centerline, last clearing of the runway and intersecting taxiways, (potential for runway incursion by taxiway or opposite direction aircraft), and mental checklist. Talking to yourself.
    ” I am ready for takeoff, AND I’M READY TO ABORT!” Only then does power go forward.
    V-1 speeds/runway position of V-1, are only rarely considered for every flight in small planes. If you are not mentally prepared to stop, you will rarely be able to quickly do it when necessity demands .
    Same thing on short final. Quick and CONSCIENCE thought, “I’m ready to land, AND PREPARED TO GO AROUND”.
    I don’t know (in forty years of instructing) how many really horrible landings I have seen when the pilot was mentally locked in to landing THEN!.

  5. Jerry Hunsinger Says:

    Thank you for your excellent article. The only statement that I take issue with is: “But it makes the case for harnesses and airbags that should be retrofitted to older aircraft and likely would have prevented most of the pilot’s injuries.”
    I own a 66-year old T-craft BC12-D and not only will I never install either shoulder harnesses or airbags – neither are called for, thankfully – but we cannot legislate safety for idiots like the pilot of the Stinson 108.

  6. Randall Henderson Says:

    The silver lining to this story is that CFIs now have an excellent tool, in the form of this video, to graphically illustrate the effects of density altitude, climbing terrain, and the benefits of safety restraints.

  7. Antonio Molinar Says:

    First I will have done and normally do is a notch of flaps, for better angle of departure.

    Second LEAN the mixture I noticed on the video it was full rich.

    I looked the area chart, there is a creek next to the airport, following it will have kept the flight from rising terrain the recommended procedure for this airport is to take off in the opposite direction

  8. Jase Valentine Says:

    Bruce,

    Strongly, near fervently, in agreement on the shoulder harness – there are a few issues I decided years ago I would maintain, and if need be, proclaim myself as a practicing coward to get the point across. Among others, military or aerobatic-grade harnesses, robust rather than minimal ELTs that ‘just meet the reg,’ bailout bags in case of unanticipated landings – even over land – I’ll even consider a ballistic chute, but only if I’m allowed to fly to the same standard I would without it(seems like more pilots with the things keep crashing in spite of it. . .) -

    All of this so I can fly relaxed and appreciative, not paranoid, and enjoy myself – all of which only works, if I keep the brain switched to the ‘Both’ position at all times. . .

    Thanks, again, Bruce./

  9. Cary Alburn Says:

    One of the first items I purchased after buying my 63 Cessna P172D 8+ years ago was BAS retracting shoulder harnesses. They had not yet been installed when I experienced a total engine failure (rod through the top of the case) and successfully landed in a field. Had the airplane nosed over, I am sure I would have been injured, wearing only the stock lap belt. In my opinion, there is little excuse for not installing some form of approved shoulder harness in every airplane’s front seats–$1000 is cheap compared to facial reconstruction surgery.

    Density altitude issues cannot be successfully taught without going to a high density altitude location. Merely reducing the throttle doesn’t mimic the lack of lift, poor climb rate or no climb rate, higher ground speed vs. IAS, etc. adequately. My initial training almost 40 years ago was at Anchorage near sea level and included mock high DA training–but when I moved to Laramie, I learned what high DA really meant. When I was instructing, all in 172s and 182s and 180hp Archers, we used to joke that 152s were great little airplanes in the winter, but all they could do was taxi fast in the summer. That’s slightly hyperbolic, but there’s a lot of truth in it.

    I have had a few high DA experiences that were my own fault for not giving DA its proper respect, fortunately without any tragic consequences, but I learned from them. Others have not been so fortunate. If this video catches the attention of enough people, perhaps high DA accidents will be reduced significantly. I’m just glad that no one died due to the pilot’s failure to give high DA its due.

  10. Tom OBryon Says:

    Glad you made it OK. Would recommend reflect on honesty. “Gust of Wind” liftoff doesn’t fly.

  11. Larry Says:

    Just climb to your airplane’s ceiling and picture yourself trying to clear a 50 foot object with the performace you have at that point.

  12. Buz Allen Says:

    One of the First things I retrofitted to my 1967 Mooney was Shoulder Harnesses! I personally don’t cherish the thought of kissing my instrument panel or the control yoke with a force of more than 2 G’s which would probably end up in the 20 to 30 G range on Impact. Early on I learned about Density Altitude and an aircraft’s ability to climb to the height above ground equal to it’s wingspan and No More, more commonly known as Ground Effect. This occurs whenever any airplane is Behind The Power Curve, even a 777. The T.O. performance figures in most multi-engine jets assume the loss of one engine for this very reason, it Happens!

  13. Eiji Hagiwara Says:

    Take a look at this picture of down burst at the left edge of developing thunderstorm. This should be included in the basic pilot training material.

  14. tamugrad07 Says:

    Eiji, where’s the link?

  15. Buzz Says:

    Once again lack of knowledge that can get you killed. In a previous post a gentleman suggests using flaps. A sure fire way to made a high density altitude takeoff worse in a lot of aircraft. Blanket procedures don’t apply for all aircraft.

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