NTSB · Safety Recommendation
Safety Recommendation A-14-109
Recommendation
TO THE FEDERAL AVIATION ADMINISTRATION: Revise the Pilot’s Handbook of Aeronautical Knowledge to clarify the information it contains on attitude indicator pitch and bank limitations to explain that attitude indicators have pitch and bank indication limits, that the pitch indicating range is required to be at least ± 25°, and that, if an aircraft operates at a pitch that exceeds the indicating limits, the pitch indicator may stop and remain at the limit until the pitch no longer exceeds the limitation, or the pitch indicator may tumble.
Safety Issue and Context
On March 30, 2013, at 2320 Alaska daylight time, a Eurocopter AS350 B3 helicopter, N911AA, impacted terrain while maneuvering during a search and rescue (SAR) flight near Talkeetna, Alaska. The airline transport pilot, an Alaska state trooper serving as a flight observer for the pilot, and a stranded snowmobiler who had requested rescue were killed, and the helicopter was destroyed by impact and postcrash fire. The helicopter was registered to and operated by the Alaska Department of Public Safety (DPS) as a public aircraft operations flight under 14 Code of Federal Regulations Part 91. Instrument meteorological conditions (IMC) prevailed in the area at the time of the accident.
The flight originated at 2313 from a frozen pond near the snowmobiler’s rescue location and was destined for an off-airport location about 16 mi south.
Response History
July 11, 2024 · NTSB Correspondence · FAA
We note that, in July 2023, you published revisions to the PHAK that include, in Chapter 8, “Flight Instruments, Attitude Indicator,” the following additional information on angle-of-attack indicators:
"The pitch and bank limits of an attitude indicator depend upon the make and model of the instrument. Some attitude indicators have limits in the banking plane from 100° to 110°, and the pitch limits can be from 60° to 70°. For those attitude indicators that display only pitch information of +/- 25° vertically, the instrument could “peg” (stop) and remain at this pitch indication until the pitch no longer exceeds limitation or ‘tumble’ and provide erroneous pitch and bank indications when the aircraft exceeds these limits. This may be extremely hazardous when the aircraft is operating in instrument meteorological conditions or confuse a pilot during an unusual attitude recovery.
A number of modern attitude indicators do not have this problem."
We believe this information is consistent with the language contained in Safety Alert for Operators 17008, “Attitude Indicator Pitch Indication Limitations,” and satisfies the intent of Safety Recommendation A-14-109. Consequently, the recommendation is classified CLOSED--ACCEPTABLE ACTION.
September 26, 2023 · Recipient Response · FAA
-From Kathryn B. Thomson, Deputy Administrator: The Federal Aviation Administration (FAA) updated the Pilot’s Handbook of Aeronautical Knowledge (PHAK) on July 10, 2023. The updated PHAK incorporates changes addressing the above safety recommendations, which include:
• A-14-109 – Chapter 8, Flight Instruments, Attitude Indicator, Page 8-19 • A-20-12 – Chapter 17, Aeromedical Factors, Drugs, Page 17-17 • A-21-20 – Chapter 14, Airport Operations, Collision Avoidance, Pages 14-28 through 14-30
The PHAK is available at the following website: https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/phak