Originally Posted by
Jambo Buana
So are you saying that current JAR states that operators may take relief from thrust reverse or not when landing on slippery runways?
Jambo, the regulation CS25 deals with aircraft certification, thus aircraft manufacturers (not operators) can apply for landing distance credit in their certified data. I do not know what the JAA 737 landing data is based on, but slide 9 suggest that reverse thrust is not included in Boeing certified data, but it is (at some undisclosed value) in the advisory data. No wonder that Boeing operators report some confusion.
It may be possible for national authorities to give operators credit for reverse thrust in ‘certificated’ operations, but I cannot give an example.
I suggest that the JAR approach in requiring certified data for contaminated runway operations is very sensible; this provides a safety margin for which recent incidents indicate is a necessity. Furthermore the problems of terminology, such as the ill defined Boeing ‘Slippery’, add confusion to contaminated runway operations and could increase risk; many of these issues are presented in
Managing the Threats and Errors during Approach and Landing.
Originally Posted by
BOAC
... the slides are lovely, but not much help in the air.
This (Boeing slide 13) is a critical point; the advisory data is based on different set of assumptions from the certification standard, thus it requires careful consideration. Since this data is more likely to be used in flight, possibly in time critical situations, then any failure to recall the differences and to carefully consider the consequences could easily result in misjudgment of braking capability on less than ideal runway surfaces. See the advice in the speakers’ notes in Slides 6/13 of Managing the Threats and Errors during Approach and Landing ref UK CAA AIC 11/98: - see all of the speakers notes for a timely pre-winter safety revision.
The bottom line for Jambo or anyone else ‘having fun’ this winter is to recall that
There is no overall accepted certification / operational correlation between mu meters and airplanes - Managing the Threats and Errors during Approach and Landing slide 26 and
Attempts to land on contaminated runways involve considerable risk and should be avoided whenever possible - UK CAA AIC 11/98.
Perhaps the final thought is for all of us is not to ask “can we undertake this operation”, but
"should we be conducting this operation".