This is an excerpt from a report made to the Aviation Safety Reporting System. The narrative is written by the pilot, rather than FAA or NTSB officials. To maintain anonymity, many details, such as aircraft model or airport, are often scrubbed from the reports.
I was flying public benefit flights in a Cessna 172 with passengers. I completed weight and balance and performance calculations before the flight and all checked out within limits.
On the takeoff roll for the first flight I noticed a much longer ground roll than I am used to and the climb was super slow at Vx (as little as 150 fpm). This put me within about 80 feet vertical of an obstacle/tower (675 AGL) we were using to navigate our route visually, and much lower than I would normally be while exiting the Delta airspace.
I noticed we were lower than I was comfortable with, so I deviated to the right and had approximately a half mile clearance from the obstacle. The rest of the flight was uneventful.
On the next flight I requested a lower passenger load that would put me even more below MTOW and again within limits. I had a better ground roll, takeoff, and climb rates of approximately 300-350 FPM, which I still was uncomfortable with.
The rest of this flight was uneventful, but due to the high density altitude I decided to call it a day and not perform further flights.
I learned that even though the performance numbers and weight and balance check out, you still may not get the performance you expect or need during high density altitude days.
I also suspect that the organization running the flights relies on self reporting of passenger weight, and I may have had a higher load than I thought I did.
In the future I will have a much higher margin below MTOW to account for this and/or use my own scale to weigh passengers.
Primary Problem: Human Factors
ACN: 2166534
When you click on the link it will take you to the ASRS Online Database. Click on Report Number and put the ACN in the search box, then click Search. On that page, click on “view only the 1 most recent report.”
Love the header. High DA and weight degrade performance. Really? Duh? Who would have thought. On anything less than a perfect day a 172 is a three person aircraft.
Never thought of it that way, but it makes sense (reduction in MTOW).
When flying around 5000’ density, altitude, airports, you need to subtract 10% of the gross weight off of your gross. This becomes your new gross operating weight.
3000 lbs-300=2,700 lbs new operating weight. When dealing with 9000 to 10000’ density altitude, airports, subtract 15% off. This because you don’t have full rated horse power. One other thing is always takeoff to Lowering train. Climb above anything you want to fly over.