Practice Problem,. Suppose the following conditions exist at B767 takeoff:

Runway Length: 12000’ Obstacle: 22000’ from the takeoff end 100’ above lowest point
Runway Temperature: 32o F (0o C)Pressure Altitude: 4000’ Runway Downslope: 2%
Conditions: 0.25” Standing WaterFlap Position: Flaps 5 A/C Packs: On
Anti-Ice: Off / Obstacle: 22000’ from the takeoff end 100’ above low point
Pressure Altitude: 4000’
Runway Downslope: 2% / Flap Position: Flaps 5
Tires: 225 mph
A/C Packs: On
10 knot tailwind
  1. Takeoff Performance Field Limit: 395,000# – 5,025# = 389,975#.

Takeoff Performance Field Limit Correction for Runway Contamination: 5,025#:

Subtract 5,700# at 380,000# gross. Subtract 4,800# at 400,000# gross.

At 395,000# gross,

Subtract = 5,700 – (0.75) (900) = 5,025#

  1. Takeoff Performance Obstacle Limit: 380,000# - 5,700# = 374,300#.

Takeoff Performance Obstacle Limit Correction for Runway Contamination: 5,700#.

Subtract 5,700# at 380,000# gross.

  1. Takeoff Performance Climb Limit: 373,000#.
  1. Takeoff Performance Tire Speed Limit Weight: 445,000# - 10 (4,300)# = 402,000# (10 kt tailwind).
  1. Maximum Authorized Brake Release Weigh is 373,000#, which is the minimum of:
  • Final Takeoff Performance Field Limit: 389,975#.
  • Final Takeoff Performance Obstacle Limit: 374,300#.
  • Takeoff Performance Climb Limit: 373,000#.
  • Takeoff Performance Tire Speed Limit: 402,000#.
  1. From Takeoff Speeds Chart, at 373,000# gross and Flaps 5:
  • Pressure altitude / temperature category is B.
  • V1 = 157 kts; VR = 160 kts; V2 = 166 kts.
  • Slope adjustment to V1 is –3 kts, and wind adjustment is –1 kts.
  • Final V1 = 157 – 3 – 1 = 153 kts. This is well above VMCG of 103 kts.
  1. Airplane is climb limited, so determine Improved Takeoff Climb Performance Limits.
  • Field Length Limit Improvement: Field Limit Weight – Climb Limit Weight = 389,975# – 373,000# = 16,975#. Climb Weight Improvement: 5,700#. Add 4 kts to V1, and 4 kts to VR and V2.
  • Tire Speed Limit Improvement: Tire Limit Weight – Climb Limit Weight = 402,000# - 373,000# = 29,000#. Climb Weight Improvement: 5,800#. Add 4 kts to V1, and 4 kts to VR and V2.
  1. Improved Takeoff Performance Climb Limit: 373,000# + 5,700# = 378,700#.
  • Add lesser of Field Length (5,700#) and Tire Speed (5,800#) Improvements to takeoff gross.
  • Improved takeoff max gross is 378,700#.
  • Add 4 kts to V1, and 4 kts to VR, and V2: V1 = 153 + 4 =157; VR = 160 + 4 = 164; V2 = 166 + 4 = 170.
  1. VMBE from Brake Energy Limit (BEL) Chart: 175 – 8 – 22 = 145 kts.
  • Decrease 8 kts for 2% downgrade.
  • Decrease 22 kts for 10 kt tailwind.
  • V1 = 157 kts and VMBE = 145 kts, so subtract 12 (800) = 9,600# from climb improved weight giving 369,100#. This exceeds actual climb improved weight ,so now apply the VMBE check to 373,000#.
  1. Determine Final Takeoff Gross and Corresponding Airspeeds:
  • Max Takeoff Gross Weight (Climb Limit) = 373,000#. Corresponding V1 = 153, VR = 160, V2= 166.
  • From BEL Chart, V1 –VMBE = 7, so must subtract 7 (1,800) = 12,600# from Takeoff Gross of 373,000#.
  • Final Max Takeoff Gross: 373,000 – 12,600 = 360,400#.
  • From Takeoff Speed Chart, V1 = 154 – 3 – 1 = 150; VR = 157; V2 = 163.

The climb limit gross was increased 5,800# using improved climb performance, then reduced since the improvement produced a V1 that exceeded VBME. We discovered that no climb improvement was possible. Finally, in fact, the original Climb Limit Gross of 373,000# was reduced (because of VBME) to 360,400#, and V1 reduced to 150 kts

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B767 Takeoff Max Gross Weight Group Exercise

Practice Problem Worksheet

You should obtain answers close to or the same as those given on the previous page

  1. Field Limit Gross
  2. Determine the uncorrected field limit gross ______#
  3. Determine the correction for runway contamination (show work) ______#
  1. Subtract b from a to determine corrected field limit gross ______#
  1. Obstacle Limit Gross
  2. Determine the uncorrected obstacle limit gross ______#
  3. Determine the correction for runway contamination (show work) ______#
  1. Subtract b from a to determine corrected obstacle limit gross ______#
  1. Determine the Climb Limit Gross ______#
  1. Tire Limit Gross
  2. Determine the uncorrected tire limit gross ______#
  3. Determine the correction for wind (show work) ______#
  1. Subtract b from a to determine corrected tire limit gross ______#
  1. Maximum Authorized Brake Release Gross (smallest of {1c, 2c, 3, 4c}) ______#
  1. Determine V1, VR, V2 associated with brake release gross
  2. Determine pressure altitude/temperature category ______
  3. Determine corresponding
  4. Uncorrected V1 ______kts
  5. VR ______kts
  6. V2 ______kts
  7. Determine V1 corrections
  8. Slope adjustment ______kts
  9. Wind adjustment ______kts
  10. Apply c to bi to determine corrected V1 (show work) ______kts
  11. Find VMCG ______kts and ensure V1 VMCG
  12. Record final V1 ______kts VR ______kts V2 ______kts

At this point you presumably have a legal max gross takeoff weight (step 5) and corresponding takeoff speeds (step 6), but you would still have to find the maximum brake energy limit speed VMBE to ensure that V1 VMBE (otherwise the brakes might overheat if you rejected the takeoff at V1). Rather than do this, we will attempt to climb improve the weight proposed in step 5.

  1. Climb Improved Max Gross: climb limit weight is lowest of field limit, obstacle limit, climb limit, and tire limit weights, so we want to climb improve the max gross takeoff weight (be sure you understand the logic of why this is possible)
  2. Climb Limit Weight (steps 3, 5) ______
  3. Subtract climb limit gross from field limit gross (show work) ______#
  1. Use b to determine
  2. Climb limit improvement corresponding to b ______#
  3. Related increments for V1 ____kts VR ______kts V2 ______kts
  4. Subtract climb limit gross from tire limit gross (show work) ______#
  1. Use d to determine
  2. Climb limit improvement corresponding to d ______#
  3. Related increments for V1 ____kts VR ______kts V2 ______kts
  1. Climb Improved Max Gross
  2. Determine climb limit improvement increment (smaller of 7ci and 7ei) ______#
  3. Find improved climb limit gross and associated takeoff speeds
  4. Add a to climb limit weight (show work) ______#
  1. Add speed increments associated with 7c or 7e (as appropriate) to the V speeds determined in 6f to get V1, VR, and V2 corresponding to 8b (show work)
  2. V1 ______kts
  3. VR ______kts
  4. V2 ______kts

At this point, you presumably have a legal climb improved max gross takeoff weight and corresponding takeoff speeds as shown in step 8. But you still have to find the maximum brake energy limit speed VMBE to ensure that V1 VMBE (otherwise the brakes might overheat if you rejected the takeoff at V1).

  1. VMBE Check for Climb Improved Weight of step 8bi
  2. Find uncorrected VMBE speed ______kts
  3. Find correction for runway gradient (show work) ______kts
  1. Find correction for wind (show work) ______kts
  1. Apply b and c to a to get corrected VMBE (show work) ______kts
  1. Compare VMBE in d to climb improvedV1 in step 8 (it’s smaller, so we have to decrease the climb improved max gross to ensures the brakes won’t overheat if we reject at V1)
  2. Subtract VMBE from V1 (show work) ______kts
  1. Find weight decrement associated with 9e1 (show work) ______#
  1. Find adjusted climb improved weight (subtract the weight decrement in ii from the climb improved weight determined in step 8) (show work) ______#

At this point, you have a max gross takeoff weight that is below the max gross takeoff weight proposed in step 5. (That is, you took off more weight in the VMBE check than you added in the climb improvement.) We will reject the attempt to climb improve, and revert to the proposed max gross takeoff weight proposed in step 5. We must still do a VMBE check for the step 5 proposed takeoff weight.

  1. VMBE Check for Step 5 Proposed Max Gross Takeoff weight
  2. Proposed takeoff gross from step 5 ______
  3. Find uncorrected VMBE speed ______kts
  4. Find correction for runway gradient (show work) ______kts
  1. Find correction for wind (show work) ______kts
  1. Apply c and d to a to get corrected VMBE (show work) ______kts
  1. Compare VMBE in 10e to V1 in step 6d (it’s smaller than V1, so we have to decrease proposed max gross takeoff weight to ensures the brakes won’t overheat if we reject at V1
  2. Subtract VMBE from V1 (show work) ______kts
  1. Find weight decrement associated with i above (show work) ______#
  1. Find adjusted gross weight (subtract weight decrement in ii from the weight determined in step 5 and transcribed to step 10a (show work) ______#

The weight in 10fiii is less than the weight in 9eiii. We accept the 10fiii weight as safer because it is lighter.

  1. Determine V1, VR, V2 associated with brake release gross in 10fiii
  2. Determine pressure altitude/temperature category ______
  3. Determine corresponding
  4. Uncorrected V1 ______kts
  5. VR ______kts
  6. V2 ______kts
  7. Determine V1 corrections
  8. Slope adjustment ______kts
  9. Wind adjustment ______kts
  10. Apply iii to ii to determine corrected V1 (show work) ______kts
  11. Find VMCG ______kts and ensure V1 VMCG
  12. Record final V1 ______kts VR ______kts V2 ______kts
  1. We will take off at the gross weight in 10fiii and use the corresponding V speeds in 10gvi. These figures are:
  • Final Proposed Max Gross Takeoff Weight ______#
  • Corresponding V1 ______kts VR ______kts V2 ______kts

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