Judd
21st Apr 2018, 13:09
Reading the magazine "Boeing Airliner" dated April 1974, there were several pages devoted to the Auto Braking system of the Boeing 747.
One paragraph caught my eye and it stated:
Q. Can early brake application cause difficulty in controlling the airplane at touchdown under adverse conditions of crosswind and slippery runways?
Answer by Boeing: "Considerable flight test experience under such conditions has shown that when testing autobrakes on the MIN and MED settings the airplane is actually more stable and controllable at touchdown than when no braking is applied.
It is true, of course, that tyre cornering is reduced during braking. However, the smooth brake application rate combined with the stabilizing effect of the brakes and the additional weight pitched forward onto the nose gear combined to more than offset any small loss in cornering.
On the MAX setting, however, the sudden hard brake application may cause a significant loss in tire cornering. Therefore, selection of the MAX setting is not recommended under adverse runway conditions."
............................................................ ........................................
While that was the Boeing position on the B747 in 1974, is the statement "Therefore, selection of the MAX setting is not recommended under adverse runway conditions," still valid now to other Boeing types? Certainly in the various B737 series FCTM, there is no mention of this recommendation that the MAX setting is not recommended under adverse runway conditions.
On the other hand, the FCTM does state if landing in a crosswind on a slippery runway and if the aircraft starts to weathercock into wind, the brakes should be released and reverse set to idle reverse until directional control is regained. But it doesn't say the MAX setting should not be selected for the landing.
Comments requested?
One paragraph caught my eye and it stated:
Q. Can early brake application cause difficulty in controlling the airplane at touchdown under adverse conditions of crosswind and slippery runways?
Answer by Boeing: "Considerable flight test experience under such conditions has shown that when testing autobrakes on the MIN and MED settings the airplane is actually more stable and controllable at touchdown than when no braking is applied.
It is true, of course, that tyre cornering is reduced during braking. However, the smooth brake application rate combined with the stabilizing effect of the brakes and the additional weight pitched forward onto the nose gear combined to more than offset any small loss in cornering.
On the MAX setting, however, the sudden hard brake application may cause a significant loss in tire cornering. Therefore, selection of the MAX setting is not recommended under adverse runway conditions."
............................................................ ........................................
While that was the Boeing position on the B747 in 1974, is the statement "Therefore, selection of the MAX setting is not recommended under adverse runway conditions," still valid now to other Boeing types? Certainly in the various B737 series FCTM, there is no mention of this recommendation that the MAX setting is not recommended under adverse runway conditions.
On the other hand, the FCTM does state if landing in a crosswind on a slippery runway and if the aircraft starts to weathercock into wind, the brakes should be released and reverse set to idle reverse until directional control is regained. But it doesn't say the MAX setting should not be selected for the landing.
Comments requested?