Boeing perf chart
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Boeing perf chart
Im trying to figure out how to use the ALT ADJ columm of the landing distance adjustment.
say field alt is 69ft and the altimeter is 1013 how would i adjust. thanks
say field alt is 69ft and the altimeter is 1013 how would i adjust. thanks
From the notes below the landing distance table:
"Reference distance is for sea level, standard day, no wind or slope...."
This is why there are adjustments (ADJ) that can be made for altitude, wind and slope.
There is also a temperature ADJ column.
The altitude adjustment is made for each 1000ft above sea level. In the table to which I am referring, the values range from 50 to 100, depending on braking action and auto brake setting, so let's assume 80.
So for an airport like Madrid, elevation 2000ft, we would add 2x80=160m to the 'Reference Distance'.
Technically speaking, the 'altitude adjustment' refers to Pressure Altitude, so you should apply a correction for high/low QNH but any resulting difference would be small when compared to the total landing distance.
In your example the QNH is 1013 so no correction for pressure altitude is necessary.
Also, the elevation is 69ft, so using sea level data would be fine.
"Reference distance is for sea level, standard day, no wind or slope...."
This is why there are adjustments (ADJ) that can be made for altitude, wind and slope.
There is also a temperature ADJ column.
The altitude adjustment is made for each 1000ft above sea level. In the table to which I am referring, the values range from 50 to 100, depending on braking action and auto brake setting, so let's assume 80.
So for an airport like Madrid, elevation 2000ft, we would add 2x80=160m to the 'Reference Distance'.
Technically speaking, the 'altitude adjustment' refers to Pressure Altitude, so you should apply a correction for high/low QNH but any resulting difference would be small when compared to the total landing distance.
In your example the QNH is 1013 so no correction for pressure altitude is necessary.
Also, the elevation is 69ft, so using sea level data would be fine.
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thanks for the reply. One more question im looking at the SLIPPERY RUNWAY TAKEOFF MAX REV THR v1(MCG) LIMIT WT CHART
how do you use this correctly? the ADJUSTED FIELD LENGHT how is that interpreted?
how do you use this correctly? the ADJUSTED FIELD LENGHT how is that interpreted?
Yes, thanks for the picture.
I think I can answer your questions but have to get some pre-flight rest now!
I will look again during my in-flight rest and write a reply then.
I think I can answer your questions but have to get some pre-flight rest now!
I will look again during my in-flight rest and write a reply then.
The purpose of this table is to determine the maximum allowed take-off weight from a slippery runway. It assumes that maximum reverse thrust is available in the event of a rejected take-off.
You have to start by knowing your airport and runway parameters and begin from 'dry' performance. This is then adjusted to allow for the actual 'slippery' conditions.
Two limiting weights will be calculated: the first to ensure that we can stop from V1 in the given length with the reduced braking action; and the second to ensure that the V1 is equal to or greater than the V1mcg. (Higher weights on a slippery runway may require a lower V1 to ensure stopping in the remaining distance.)
The 'slippery runway limited weight' will be the lower of these two weights.
a) Let's assume a sea-level airport with a 7,160ft runway. OAT is -6C. Reported braking action is POOR.
b) Start by calculating a 'dry' TOPL weight for the runway in question using the normal performance process. Let's assume this is 160,000lbs.
c) Enter the 'Weight Adjustment' table (the upper of the two tables) with the pressure altitude (S.L.) for the reported braking action (POOR) and the 'dry' TOPL (160). This yields a slippery runway weight adjustment of -18,300lbs, resulting in a 'slippery' TOPL of 141,700lbs.
d) Next we have to adjust the 7,160ft 'dry' available runway length for braking action and OAT. The note 2 at the bottom of the tables tells us to adjust the 'POOR' field length by +120ft for every 5C below 4C. Our OAT is -6C so we will add 240ft to the 7,160ft 'dry' length, giving 7,400ft.
e) Now we have to find the V1mcg limited weight. Enter the lower table with the adjusted field length (7,400) and pressure altitude (S.L.) for the reported braking action (POOR). This gives a weight of 179,300lbs.
f) The maximum allowed 'slippery runway limited weight' is the lower of 141,700lbs and 179,300lbs = 141,700lbs.
For another example, let's take an airport at an elevation of 5,000ft. The OAT is +9C, braking action is MEDIUM and the runway is 5,460ft long. 'Dry' TOPL is 146,000lbs.
Weight adjustment is -10,000lbs, giving a 'slippery' TOPL of 136,000lbs.
Adjust MEDIUM field length by -60ft, giving 5,400ft.
V1mcg limited weight is 134,500lbs. This is lower than the 'slippery' TOPL so the maximum allowed 'slippery runway limited weight' is 134,500lbs.
You have to start by knowing your airport and runway parameters and begin from 'dry' performance. This is then adjusted to allow for the actual 'slippery' conditions.
Two limiting weights will be calculated: the first to ensure that we can stop from V1 in the given length with the reduced braking action; and the second to ensure that the V1 is equal to or greater than the V1mcg. (Higher weights on a slippery runway may require a lower V1 to ensure stopping in the remaining distance.)
The 'slippery runway limited weight' will be the lower of these two weights.
a) Let's assume a sea-level airport with a 7,160ft runway. OAT is -6C. Reported braking action is POOR.
b) Start by calculating a 'dry' TOPL weight for the runway in question using the normal performance process. Let's assume this is 160,000lbs.
c) Enter the 'Weight Adjustment' table (the upper of the two tables) with the pressure altitude (S.L.) for the reported braking action (POOR) and the 'dry' TOPL (160). This yields a slippery runway weight adjustment of -18,300lbs, resulting in a 'slippery' TOPL of 141,700lbs.
d) Next we have to adjust the 7,160ft 'dry' available runway length for braking action and OAT. The note 2 at the bottom of the tables tells us to adjust the 'POOR' field length by +120ft for every 5C below 4C. Our OAT is -6C so we will add 240ft to the 7,160ft 'dry' length, giving 7,400ft.
e) Now we have to find the V1mcg limited weight. Enter the lower table with the adjusted field length (7,400) and pressure altitude (S.L.) for the reported braking action (POOR). This gives a weight of 179,300lbs.
f) The maximum allowed 'slippery runway limited weight' is the lower of 141,700lbs and 179,300lbs = 141,700lbs.
For another example, let's take an airport at an elevation of 5,000ft. The OAT is +9C, braking action is MEDIUM and the runway is 5,460ft long. 'Dry' TOPL is 146,000lbs.
Weight adjustment is -10,000lbs, giving a 'slippery' TOPL of 136,000lbs.
Adjust MEDIUM field length by -60ft, giving 5,400ft.
V1mcg limited weight is 134,500lbs. This is lower than the 'slippery' TOPL so the maximum allowed 'slippery runway limited weight' is 134,500lbs.
