Centaurus
2nd Mar 2011, 11:45
The Boeing 737 Flight crew Training Manual (FCTM) under the heading of Callouts, states: "The PM calls out significant deviations from command airspeed or flight path." It is left to the operator to define how this is done. Perhaps the most common expression for significant airspeed deviations from the norm is "SPEED" called by the PM. The speed tolerance is up to the operator and is defined in the company FCOM.
Recent incidents/accidents where erroneous flight instrument indications have been suspected, suggest that airspeed indications between captain and first officer airspeed indicators and possibly the standby ASI, have differed, leading to uncertainty and confusion.
"SPEED" as a support call from the PM usually means the PF is out of tolerance. But to what extent and in what direction - too fast or too slow? Perhaps "Speed fast" or "Speed slow" would be more precise - especially if an erroneous airspeed indication was the problem. A quick glance at the third ASI as the umpire, may help clarify things promptly -assuming that ASI is unaffected because of its different information source. This is the reason for the third ADI - to act as umpire.
A call of "SPEED FAST" from the PM would hopefully immediately prompt a query from the PF, if his own ASI was indicating correctly to his eyes.
In the early days of the 737-100/200, Boeing recommended (for the approach and landing case) the airspeed support call be based upon the planned Vref speed. For example "Vref plus 15." This policy was based upon the fact that anything faster than Vref at the threshold would extend the landing distance. The current limit of Vref plus 20 knots is till the upper figure beyond which the potential for an over-run beyond the scheduled landing distance becomes serious.
A planned approach speed of Vref plus 20 knots (this would generally mean headwind component and gust additives combined) would not be subject to a out of tolerance support call if the airspeed was within company tolerance. Nevertheless a heightened sense of speed awareness engendered by reference to Vref would surely be good airmanship - particularly if runway length limited or wet surface.
Thus, two knots over the additives doesn't sound very much - but a support call of "Vref Plus 22 knots" puts a whole new urgency into the support call. A call of "SPEED" by itself becomes meaningless.
Many years ago, an airline in Australia introduced a support call at 500 feet above airfield elevation, of airspeed deviation above Vref and rate of descent. This was intended to remind the crew of the lower limit of stabilisation on final, whether IMC or visual. A typical call by the PM would be "500 feet - Vref plus 12 - Sink 800." The call emphasised the airspeed above Vref - not the airspeed above the Vref plus additives. "Bug plus 2" sounds positively benign in meaning, when compared with "Vref plus 22"
Regardless of company policy on speed tolerances before a warning (support) call is warranted, "SPEED FAST" or "SPEED SLOW" is more precise that the one word "SPEED." It also has the added advantage of quickly picking the onset of erroneous airspeed indications.
Recent incidents/accidents where erroneous flight instrument indications have been suspected, suggest that airspeed indications between captain and first officer airspeed indicators and possibly the standby ASI, have differed, leading to uncertainty and confusion.
"SPEED" as a support call from the PM usually means the PF is out of tolerance. But to what extent and in what direction - too fast or too slow? Perhaps "Speed fast" or "Speed slow" would be more precise - especially if an erroneous airspeed indication was the problem. A quick glance at the third ASI as the umpire, may help clarify things promptly -assuming that ASI is unaffected because of its different information source. This is the reason for the third ADI - to act as umpire.
A call of "SPEED FAST" from the PM would hopefully immediately prompt a query from the PF, if his own ASI was indicating correctly to his eyes.
In the early days of the 737-100/200, Boeing recommended (for the approach and landing case) the airspeed support call be based upon the planned Vref speed. For example "Vref plus 15." This policy was based upon the fact that anything faster than Vref at the threshold would extend the landing distance. The current limit of Vref plus 20 knots is till the upper figure beyond which the potential for an over-run beyond the scheduled landing distance becomes serious.
A planned approach speed of Vref plus 20 knots (this would generally mean headwind component and gust additives combined) would not be subject to a out of tolerance support call if the airspeed was within company tolerance. Nevertheless a heightened sense of speed awareness engendered by reference to Vref would surely be good airmanship - particularly if runway length limited or wet surface.
Thus, two knots over the additives doesn't sound very much - but a support call of "Vref Plus 22 knots" puts a whole new urgency into the support call. A call of "SPEED" by itself becomes meaningless.
Many years ago, an airline in Australia introduced a support call at 500 feet above airfield elevation, of airspeed deviation above Vref and rate of descent. This was intended to remind the crew of the lower limit of stabilisation on final, whether IMC or visual. A typical call by the PM would be "500 feet - Vref plus 12 - Sink 800." The call emphasised the airspeed above Vref - not the airspeed above the Vref plus additives. "Bug plus 2" sounds positively benign in meaning, when compared with "Vref plus 22"
Regardless of company policy on speed tolerances before a warning (support) call is warranted, "SPEED FAST" or "SPEED SLOW" is more precise that the one word "SPEED." It also has the added advantage of quickly picking the onset of erroneous airspeed indications.