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<Answer>. No, the FMC does not display flight technical error. We do not consider it necessary to
monitor cross track error.
60. Why does Boeing recommend MDA + 50 used as the DA?
<Answer>. Boeing has determined that an additive of 50 feet above the published MDA(H) is
adequate to comply with the MDA(H) when on a constant angle approach and a missed
approach is initiated at MDA(H) + 50 feet
61. When do you set MDA?
<Answer>. Set MDA in the AFDS mode control panel just prior to selecting VNAV to commence
the final approach. This is done by Boeing procedures when approximately 2 NM prior
to the FAF or final approach segment.
62. If, for example, we have a DA of 640 feet, what should we set the MCP altitude to?
<Answer>. As in A60, set MCP to the next lower altitude number, in this case 600 feet. Once
established on final approach in the descent, and at least 300 feet below the missed
approach altitude, set the MCP to the missed approach altitude.
2004 Flight Operations Symposium Questions 8/23/2004 10:19 AM
May 9 – 12, 2004, Bell Harbor Convention Center
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63. The 757 AFM has a requirement (limitation?) for 250 ft AGL or 5000 RVR…. What is the history
behind the 5000 ft RVR requirement?
<Answer>. We have not been able to locate the noted requirement (limitation) in the 757 AFM.
64. Should the green arc be used to determine if the airplane is on the proper flight path to arrive at
the runway?
<Answer>. While the MCP is set at MDA(H) the green arc will indicate where the airplane will
arrive at the MCP altitude, but this indication may be of questionable value in turbulence
and will not be available once the MCP altitude is reset to the missed approach altitude.
If flying final approach in VNAV PTH, this technique for monitoring path performance is
not necessary.
65. Some airlines were advocating setting the field elevation in the MCP during the approach and
then using the green arc as a cross check to ensure they were on the proper path.
<Answer> This isn’t recommended. If a windshear is encountered during the approach the autopilot
could capture the field elevation if the airplane was 800 ft AGL at some point during the
maneuver. This is also unnecessary once in VNAV PTH mode on final approach.
66. Does the green arc show the next altitude or the runway end?
<Answer> The green arc remains only where the MCP is set and provides a prediction of point of
arrival at the MCP altitude. There is no need to keep the green arc once the airplane has
captured the path.
67. The RDMI pointer points to the next waypoint in MAP mode, so how does this relate to the AFM?
We are not meeting the first AFM requirement to monitor raw data.
<Answer>. Your unique airplane configuration is certified for this operation. There is no need to
monitor raw data.
68. If ILS or LOC+DME do you need DME update?
<Answer> RNP operations do not require DME or timing, however we encourage monitoring raw
data if it is available.
69. Are the altitude and temperature corrections on the Legs page?
<Answer> If cold temperature altitude corrections are made, normally the crew would at least add
the correction to the FAF (and if needed the IAF or transition altitude) waypoint altitude
constraints.
70. Please explain the AFM limitation which does not allow use of LNAV or VNAV with QFE?
<Answer> The FMC navigation database is coded by mean sea level (MSL), so there will be vertical
error if VNAV is used during QFE operation. The use of LNAV is restricted during QFE
2004 Flight Operations Symposium Questions 8/23/2004 10:19 AM
May 9 – 12, 2004, Bell Harbor Convention Center
Page 12 of 15
operation because of the possibility of altitude-based constraints associated with
conditional waypoints in a selected departure, arrival or missed approach procedure.
71. Does changing the altitude on a waypoint affect the approach logic?
<Answer>. No, it does not.
72. Will temperature corrections to waypoint altitude adversely affect the approach?
<Answer> No assuming the correction is appropriate for the temperature and height above the
airport. A Statement from the floor said that Transport Canada mandates a temperature
correction.
73. Is there a limitation in QFE for LNAV below transition altitude?
<Answer>. Yes. See A70 above.
74. Is there a time limit on how soon before commencing the approach DME-DME updating must be
checked?
<Answer>. No, the AFM simply says "prior to approach."
An Enhanced Boeing QRH:
75. We like the sample checklist with conditional statements and the choices, but what about a
　
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