.
Plan to land at the nearest suitable airport
-Crosswind capability may be reduced
.
Do not turn off any Flight Control Switches
.
Plan a flaps 15 landing
.
Use VREF 15 + 5 or VREF ICE + 5
.
Place the GROUND PROXIMITY FLAP INHIBIT Switch to FLAP INHIBIT
Flight Crew Operations Manual Bulletin No. SHZ-30, dated September 16, 2002 (continued)
Administrative Information
Insert this bulletin behind the FCOM Bulletin Record Page in Volume 1 of your FCOM. Amend the FCOM Bulletin Record Page to show Bulletin SHZ-30 "IN EFFECT" (IE)
This bulletin will be cancelled after Boeing has been notified that no suspect flight control modules are installed in any airplanes in your fleet.
Please send all correspondence regarding FCOM bulletin status to one of the
following addresses:
Mailing Address: Manager 737, Flight Technical Integration & Data Boeing Commercial Airplane Group P. O. Box 3707 MS 20-89 Seattle, WA 98124-2207 USA
Fax Number: Telex: SITA: E-MAIL: (206) 662-7812 329430 Station 627 LKEBO7X FTID@Boeing.com
Flight Crew Operations Manual Bulletin
for
The Boeing Company Seattle, Washington 98124-2207
737
Number: SHZ-32 R1 Date: November 01, 2004 Document Effectivity:
Subject: Target Speed Anomaly with Flaps Extended and VNAV Engaged
Reason: This bulletin informs flight crews of target speed anomalies on airplanes equipped with the Collins Enhanced Digital Flight Control System (EDFCS) when flaps are extended and operating in VNAV. The purpose of this reissue is to provide Service Bulletin information.
Information in this Flight Crew Operations Manual (FCOM) bulletin is recommended by The Boeing Company, but may not be FAA approved at the time of writing. In the event of conflict with the FAA approved Airplane Flight Manual (AFM), the AFM shall supersede. The Boeing Company regards the information or procedures described herein as having a direct or indirect bearing on the safe operation of this model airplane.
THE FOLLOWING PROCEDURE AND/OR INFORMATION IS EFFECTIVE UPON RECEIPT
Background Information
Boeing has received reports of target speed anomalies with flaps extended when operating in VNAV during approach. The anomaly may occur at any flap setting from Flaps 2 to Flaps 40, but the discrepancy is most likely to occur at Flaps 15 due to system tolerances.
The Flight Management Computer (FMC) uses flap position data as output by the Flight Control Computer (FCC). Due to an implementation error in the Collins Enhanced Digital Flight Controls System (EDFCS), the FCC sends uncorrected flap position data rather than adjusted data. The FMC switches to the next higher flap setting when it receives a signal that the flap position has increased more than 0.5 degrees above the selected flap detent. With the flap handle at Flaps 15, the uncorrected flap position data may be as high as 19.5 degrees depending on airplane installation and tolerances. Similar differences between uncorrected and adjusted data exist for other flap settings, but the system tolerances are much smaller. As a result, the anomaly is less likely to occur at flap settings other than Flaps 15.
Flight Crew Operations Manual Bulletin No. SHZ-32 R1, dated November 01, 2004 (continued)
When Flaps 15 is selected, the target speed initially indicates the correct airspeed for the flap setting as the flaps transition from 10.5 to 15 degrees. If the tolerances at this flap setting result in an uncorrected output greater than 15.5 degrees, the target speed (magenta bug) may reduce to a speed consistent with Flaps 25 and the autothrottles will adjust to capture this lower speed. This results in the aircraft slowing to near minimum maneuver speed for Flaps 15.
When flying a VNAV approach on airplanes equipped with speed intervention (SPD INTV), the flight crew should select SPD INTV prior to the initial flap selection and manually set the correct flap speed on the MCP. The autothrottles will adjust to capture the MCP speed. SPD INTV should be used for the duration of the approach.
On airplanes without speed intervention, VNAV must be disengaged and the approach flown in another mode if the anomaly is observed. When landing flaps are selected, VNAV may be re-engaged.
On airplanes equipped with the Head-Up Display (HUD), the AOA approach band may not be correctly displayed with Flaps 15 selected. When Flaps 30 or 40 have been selected, the AOA approach band will be correctly displayed on the HUD.
This anomaly will be corrected in a future FCC software upgrade targeted for early 2004.
Operating Instructions
When flying VNAV approaches on airplanes equipped with speed intervention (SPD INTV), select SPD INTV prior to the initial flap selection and manually select the correct speed on the MCP. Remain in SPD INTV for the duration of the approach.
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