Originally Posted by
MysteriousMrX
Had a flight the other day (fly CRJ-900) ..
Dispatch paperwork said planned takeoff weight was something like 74,200 lbs. Max takeoff weight 79,000lbs, roughly.
Loaded the numbers into ACARS.. said our weight was about 74.2.. as planned.. however it said our max weight was 74.7 or something like that. Why?
Am I missing something basic here? Let’s say we had extra bags and were overweight? We can’t go....
Your structural max takeoff weight is 84,500. The 79,000 is probably max landing weight plus fuel burn. Was your fuel burn about 3,900? If you took off at a higher weight, you would be overweight for landing. The 74.7 is probably based on a FLX temp (although flaps 8 vs 20 could be an additional factor). If you were to select NO FLEX, AeroData (ACARS) would probably come back with a higher weight. Entering a higher weight would also likely give you good data with a resultant increase in take off N1 (Lower flex temp or even full thrust)
What might be causing some confusion is that there are several different takeoff weights listed in different places throughout a release:
Max structural: 84500 for CRJ 900
Manufacturers performance baseline (my term): often several thousand pounds higher than even max structural
Max flight plan: The most you can takeoff with (considering planned fuel load and burn) and not exceed other weight limitations (usually landing weight, but I'm sure a scenario containing ramp weight or ZFW could be created)
Planned takeoff: Usually right at your planned weight, often with an extra line for 1000/2000# over that. This is where you get your numbers for takeoff if your ACARS is inop.
All of these will make some reference to MAX, TAKEOFF, and WEIGHT, but they are not the same.
In your initial scenario, it is possible that 79,000 was your max flight plan takeoff weight (for max landing weight) and 74.7 was your planned takeoff weight. Maybe there was another line for plus 1000#. Even if there wasn't, you could call dispatch and have them send you a new release with higher numbers.
Originally Posted by
MysteriousMrX
Other question, re: required landing length.
We need a certain length to stop the aircraft, but we add 60% to be legal and safe. ACARS will say our min length is, let’s say 3000’ but 4800’ is the required. SO, if you if you get let’s say, a Spoileron fail caution or whatever, you add 20% to the landing distance. Is that 20% of the lower or higher number?...
Again, this is a situation that requires attention to detail. Your QRH most likely references Actual Landing Distance. In that case you would determine Actual Landing Distance (probably from your speed book) and add the 20%. Minimum Landing Distance is a different number (without looking it up, I believe it is a factored number used for dispatch legalities). However, some airlines also require you use a Minimum Field Length number to land (ie, you can't use Actual Landing Distance for normal operations). Using the QRH waives that requirement in most cases.
Best advice: Read the related sections (Performance/Release/Loading/Etc) of your GOM/FOM and your POH/FCOM. Read the QRH items in question. Read them all in detail. Small words make big differences. Also might not hurt to ask other pilots. Like has been said previously, this should have been covered in initial. It will definitely be covered in the upgrade oral/KV.