PPRuNe Forums Braking system efficiency - Loss of braking - wet runway

 Flight Testing A forum for test pilots, flight test engineers, observers, telemetry and instrumentation engineers and anybody else involved in the demanding and complex business of testing aeroplanes, helicopters and equipment.

18th Jan 2011, 16:21   #1 (permalink)

Join Date: Aug 2005
Location: Europe
Posts: 97
Braking system efficiency - Loss of braking - wet runway

Quote:
 Determine estimated aircraft tire effective braking coefficient µ eff by using the following equations: µ eff = 0.2 µ max + 0.7 µ max2 (µ max less or equal to 0.7) (4a) µ eff = 0.7 µ max for µ max (µ max greater than 0.7) (4b) These relationships between aircraft tire maximum braking and effective braking friction coefficient are based on the assumption that the total aircraft braking-system (tires, brakes, hydraulics, gear and antiskid efficiency can be generated by a single curve 4(a) and (b)
The above is quoted from the report: NASA Technical Paper 2917 - Evaluation of Two Transport Aircraft and Several Ground Test Vehicle Friction Measurements Obtained for Various Runway Surface Types and Conditions - A Summary of Test Results From Joint FAA/NASA Runway Friction Program, February 1990

Aircraft used B727 and B737

How relevant are these equations for todays braking systems (more than 20 years later)?
What level of uncertainty do the assumption tires, brakes, hydraulics, gear and antiskid efficiency can be generated by a single curve represent?

 18th Jan 2011, 19:49 #2 (permalink) Join Date: Dec 2002 Location: UK Posts: 1,120 Current certification aspects are in CS 25.109 where there are vaguely similar equations. Some of the flight test assumptions are in AMC 25.109 para 3.5. “The tyres and brakes should not be new, but need not be in the fully worn condition. They should be in a condition considered representative of typical in-service operations”. Anti-skid efficiency is discussed in para 3, (92% max), and the runway surface in para 3.3, which should be smooth. Porous runways are discussed in 109 (d) 2 There are references to ESDU 71026 for braking coefficient of friction: IHS ESDU 71026 IHS ESDU 95015 Also, see www.spaceagecontrol.com/AC25-7A.pdf references to 25.109

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are Off Pingbacks are Off Refbacks are Off Forum Rules

All times are GMT. The time now is 08:02.