Question: Is there anything in writing that gives the reason for not using the autopilot for a single-engine approach and what is the reason for no doing so? It can be used after clean up on an engine failure after takeoff with the 970 and 971 computer.

Answer: No. Autocoupled ILS approaches with one engine inoperative have not been demonstrated, therefore the aircraft is not certified for such a procedure.

A single-engine LOC only and vertical speed mode of operation to LOC minimums (or 50 feet below MDA as authorized by the FAR) is legal. It is not a prudent procedure to take manual control of an aircraft at the minimum descent altitude. It denies the pilot the “feel” of the aircraft in sufficient time to ensure good control and a safe landing. Retrimming may be necessary when the autopilot is dis-engaged. Yaw displacement occurring at dis-connect can easily disrupt the localizer alignment and cause the aircraft to deviate from course. What usually follows is a wing down lateral correction late in the approach to regain the localizer which can be especially hazardous in reduced visibility, at night and/or gusty crosswinds.

Given the above, Douglas does not recom-mend a coupled LOC only, vertical speed mode approach with an engine inoperative.

Question: What are the crosswinds limits?.

Answer: It is the practice of the FAA and this office, to conduct type certification flight test to establish crosswind component ve-locities that assure safe takeoff and landing operations on dry runways in accordance with the requirements of Section 25.237 (a) of Part 25 of the FAR. In amplifying the method of demonstrating compliance with this requirement, Paragraph 30e(2)(ii) of Ad-visory Circular 25-7 states, “For each test condition a qualitative evaluation by the pilot of airplane control capability, forces, airplane dynamic reaction in gusty crosswinds.... and general handling characteristics should be conducted....Wind data from INS systems, tower or portable ground recording stations should be corrected to a 90-degree cross-wind component and to a height of 10 me-ters.” Section 25.1587(b) of FAR 25 states, “Each Airplane Flight Manual must contain the performance information....for the weights, altitudes, temperatures wind com-ponents, and runway gradients, as applica-ble, within the operational limits of the air-plane...”.

Douglas Aircraft Company has demonstrated crosswind operations to the FAA for each of their certificated aircraft. The performance sections of the FAA approved AFM provide the highest crosswind components demon-strated to the FAA which have been found to permit safe controllability. Despite the fact that these crosswind components are not considered to be limiting because no control-lability limitations were observed during the flight test, such controllability limits were closely approached. Any proposed increases in approved crosswind components would have to be evaluated under controlled test conditions. Although operators of foreign-registered aircraft may seek such increases from their national civil aviation authorities, the FAA would not approve operation in greater crosswinds without additional type certification flight testing.

Question: The procedure in the FCOM for a STALL INDICATION FAILURE LIGHT ON, direct the crew - when flight conditions permit - to OPEN (PULL) the Captain’s/First offi-cer’s Stall Warning C/Bs on the lower EPC. Our Flight Crew Training has pointed out that there are two (2) sets of C/Bs on the lower EPC:

EPC LOCATION DESCRIPTION
P-35 Stall warning and Auto Slat-1
R-35 Stall Warning and Auto Slat-2
X-23 Captain’s Stall Warn-ing
Z-23 First Officer’s Stall Warning

Note: Individual operators may find that C/B locations vary.

To aid in quickly identifying these C/Bs, we have installed collars on P-35 and R-35. Flight Crew Training and Engineering believe that the correct C/Bs to open during the ref-erenced abnormal procedure are C/Bs X-23 and Z-23.

Please advise which are the correct C/Bs. Is it acceptable to install “ID” collars for quick identification of C/Bs?.

Answer: The STALL INDICATION FAIL-URE LIGHT ON procedures states that C/Bs X-23 and Z-23, the Captain’s/First Officer’s Stall Warnings are opened (PULLED)
These C/Bs control the respective stall warning computers.

C/Bs P-35 and R-35 provide power for the autoslat extend and stick pusher and should not be opened with this abnormal procedure.

DAC does not install collars for the purpose of identification. Maintenance on occasion, does use collars to identify disabled circuits. However, many operators use collars (Chicken Rings) to identify specific C/Bs.