A-81-104
NTSB Safety Recommendation — Aviation
Recommendation text
THE NTSB RECOMMENDS THAT THE FEDERAL AVIATION ADMINISTRATION: INCORPORATE THE FOLLOWING INFORMATION INTO THE DC-9-80 AIRCRAFT FLIGHT MANUAL UNDER THE ABNORMAL HYDRAULICS-OUT LANDING SECTION AND THE NORMAL LANDINGS ON WET/SLIPPERY RUNWAYS SECTION: THE MAXIMUM RUDDER EFFECTIVENESS AVAILABLE IS SUBSTANTIALLY REDUCED DURING REVERSE THRUST OPERATION AS FOLLOWS: ENGINE THRUST MAXIMUM RUDDER SETTING EFFECTIVENESS AVAILABLE(PERCENT)*/ FORWARD IDLE 100 REVERSE IDLE 65 1.3 EPR (REVERSE) 25 1.6 EPR (REVERSE) MINIMAL */RUDDER EFFECTIVENESS ALSO DECREASES WITH DECREASING AIRSPEED. WHEN REVERSE THRUST LEVELS ABOVE REVERSE IDLE ARE USED, CAREFULLY MONITOR AND MAINTAIN SYMMETRIC REVERSE THRUST TO AVOID ADVERSE YAWING MOMENTS.
In plain language (FlightFinder summary)
The FAA is asked to add to the DC-9-80 flight manual, under the abnormal hydraulics-out landing and normal wet/slippery runway sections, a table showing that maximum rudder effectiveness is substantially reduced during reverse thrust—for example, dropping from 100% at forward idle to minimal at 1.6 EPR reverse. The manual should also note that rudder effectiveness decreases with airspeed and that above reverse idle, symmetric reverse thrust must be monitored to avoid adverse yaw.
This plain-language summary is written by FlightFinder to explain the recommendation above. It is not the official wording — the verbatim NTSB text is quoted above.
Details
| Status | Closed - Acceptable Alternate Action |
|---|---|
| Mode | Aviation |
| Closed | May 29, 1984 |
| NTSB number | LAX80FA111 |
| Addressees | FAA |
External links
NTSB safety recommendations are advisory; addressees are not legally required to adopt them. Source: NTSB CAROL (public domain).