JARs RLD vs ALD
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JARs RLD vs ALD
Trying to get some sense out of JARs in relation to wet runways...
ALDdry allows no credit for reversers.
RLDdry , and RLDwet are both functions of ALDdry .
Therefore it seems no reverse credit is given for either of these cases (according to JARs). The a/c manuals (a/c certified under JARs) show conflicting info.
Can anyone clarify for me please?
ALDdry allows no credit for reversers.
RLDdry , and RLDwet are both functions of ALDdry .
Therefore it seems no reverse credit is given for either of these cases (according to JARs). The a/c manuals (a/c certified under JARs) show conflicting info.
Can anyone clarify for me please?
Last edited by jtr; 5th Jun 2005 at 03:01.
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ALDdry doesnot take credit of the reverse, that doesn´t mean that it use is forbiden. So if we use reverses our ALD will be shorter than calculated, and this is good for us.
JAR OPS 1.515 (A) RLD dry= ALD/0.6
JAR OPS 1.520 RLD wet= 1.15 RLD dry
JAR OPS 1.520 RLD cont= the greatest of 1.15 ALD cont/ RLD wet.
ALD cont is calculated with reverses.
ONE EXAMPLE:
ALD dry: 1200m ( no reverses)
ALD on dry runway using reverses: 950 m.
RLD dry: 2000m, minimum LDA to land legally. IF reverses are used 1050 m are left unused (better for us), if you land without reversers only 800m are left.
According JAR 25.125 braking means other than wheel breaks, e.g. reversers can be used when they are safe and reliable (except on dry runway), for determine the ALD.
So,
"ALD" on wet without reversers 1400m, with reversers 1300m
RLD dry (no reverse) 2000m, RLD dry with reverses the same and
RLD wet= 1.15 *2000m= 2300m. IF you use the reversers 1.000m are not used, without them 900m.
ALD cont ( using reversers)= 1850m for the type and depht of contaminant.
RLD cont= the gratest of:
1.15 ALD cont= 1.15*1850= 2.127 m
RLD wet= 2300m.
In this case RLD cont= 2300m
So finally, ALD cont (1850M) is the 80% of the RLD 2300m.
JAR OPS 1.515 (A) RLD dry= ALD/0.6
JAR OPS 1.520 RLD wet= 1.15 RLD dry
JAR OPS 1.520 RLD cont= the greatest of 1.15 ALD cont/ RLD wet.
ALD cont is calculated with reverses.
ONE EXAMPLE:
ALD dry: 1200m ( no reverses)
ALD on dry runway using reverses: 950 m.
RLD dry: 2000m, minimum LDA to land legally. IF reverses are used 1050 m are left unused (better for us), if you land without reversers only 800m are left.
According JAR 25.125 braking means other than wheel breaks, e.g. reversers can be used when they are safe and reliable (except on dry runway), for determine the ALD.
So,
"ALD" on wet without reversers 1400m, with reversers 1300m
RLD dry (no reverse) 2000m, RLD dry with reverses the same and
RLD wet= 1.15 *2000m= 2300m. IF you use the reversers 1.000m are not used, without them 900m.
ALD cont ( using reversers)= 1850m for the type and depht of contaminant.
RLD cont= the gratest of:
1.15 ALD cont= 1.15*1850= 2.127 m
RLD wet= 2300m.
In this case RLD cont= 2300m
So finally, ALD cont (1850M) is the 80% of the RLD 2300m.
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Thanks, so to further explain what this I am getting at...
RLDwet makes no allowance for reverser use.
ALDwet does make allowance for reverser use.
Just seems odd to me (well odder than most other things in JARs is what I mean), and more specifically, conflicts with the allegedly JARs certified info in the AFM we use.
RLDwet makes no allowance for reverser use.
ALDwet does make allowance for reverser use.
Just seems odd to me (well odder than most other things in JARs is what I mean), and more specifically, conflicts with the allegedly JARs certified info in the AFM we use.
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Remember that "ALD wet" is not defined by regulations.
RLD wet= 1.15 RLDdry makes no allowance for reversers, but if you have then use them, good for you. Your "real" landing distance will be shorter than expected and calculated by regulations.
ALD wet is not defined by regs, ALDwet= ALD dry that is the reason for the 15% increment for RLD calculations. But anyhow the "real" distance when landing on wet can be measured with and without reversers.
This regulations are giving safer margins for pilots and do not preclude the use of reversers if available. Under my point of view there is no conflict.
RLD wet= 1.15 RLDdry makes no allowance for reversers, but if you have then use them, good for you. Your "real" landing distance will be shorter than expected and calculated by regulations.
ALD wet is not defined by regs, ALDwet= ALD dry that is the reason for the 15% increment for RLD calculations. But anyhow the "real" distance when landing on wet can be measured with and without reversers.
This regulations are giving safer margins for pilots and do not preclude the use of reversers if available. Under my point of view there is no conflict.
