B737 perf
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B737 perf
Hello guys,
I was just looking at the B737 perf especially on contaminated and slippery runway.
If someone has seen them, maybe he can answer me:
1- For the V1(MCG) limit weight table (Slush/standing water/max rev):
The limit weight will increase when the runway length increases (OK)
But I do not understand why the limit weight does not increase when altitude pressure increases.....I was thinking that the increase of altitude pressure will result in lower VMCG, V1 could be further reduced and limit weight would be increased. What's wrong with my reasoning?
The approx max TOW of the B737 800 being 80T, why bother putting such values as 102.8T in the table (2000m, 5000ft, 3mm)
2- V1 adjustment table (slush/standing water/max rev):
Values of V1 adjustment will decrease as the pressure altitude increases, I understand that as a loss of thrust due to the decreased pressure so we have to keep the TOD within TODA.
However I do not understand why the V1 adjustment decreases as the weight decreases (90T, SL, 3mm = -12kts ; 40T, SL, 3mm= -25kts)
3- V1(MCG) limit weight table ( slush/standing water/NO REV)
Figures are different depending on conditions, however there are only a few ones
At SL and for 3mm, for instance, you will find only 3 figures for all runway lenghts : 33.1, 66.9, 104.7. Figures are just offset when you change the pressure altitude
Why such similarities?
Thank you in advance
I was just looking at the B737 perf especially on contaminated and slippery runway.
If someone has seen them, maybe he can answer me:
1- For the V1(MCG) limit weight table (Slush/standing water/max rev):
The limit weight will increase when the runway length increases (OK)
But I do not understand why the limit weight does not increase when altitude pressure increases.....I was thinking that the increase of altitude pressure will result in lower VMCG, V1 could be further reduced and limit weight would be increased. What's wrong with my reasoning?
The approx max TOW of the B737 800 being 80T, why bother putting such values as 102.8T in the table (2000m, 5000ft, 3mm)
2- V1 adjustment table (slush/standing water/max rev):
Values of V1 adjustment will decrease as the pressure altitude increases, I understand that as a loss of thrust due to the decreased pressure so we have to keep the TOD within TODA.
However I do not understand why the V1 adjustment decreases as the weight decreases (90T, SL, 3mm = -12kts ; 40T, SL, 3mm= -25kts)
3- V1(MCG) limit weight table ( slush/standing water/NO REV)
Figures are different depending on conditions, however there are only a few ones
At SL and for 3mm, for instance, you will find only 3 figures for all runway lenghts : 33.1, 66.9, 104.7. Figures are just offset when you change the pressure altitude
Why such similarities?
Thank you in advance
Join Date: Jun 2000
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The approx max TOW of the B737 800 being 80T, why bother putting such values as 102.8T in the table (2000m, 5000ft, 3mm)
Your whole post needs some brain scratching and deep consideration. A quick answer to this question is:
slippery runway adjustments are for performance possibilities not structural weight. You find out what is theoretically the maximum possible and make deductions from that. You may then find that you can still go at max structural. Although 102.8T for B737 does seem fanciful as a start point for 2000m Maybe they have 40k engines.
However, not using max structural weight gives more correct runway performance calculations. This was well demonstrated by one fledgling airline I was with. Their performance dept did just this. The RTOW table topped out at the certified max structural of the fleet. Thus the MTOW dry on a 2500m runway & 3000m runway were the same. When you started making various deductions for go/stop calculations, be it technical or contaminated, you found from a 3000m runway you couldn't make destination fuel, but the local more established airline had no bother. Eyes opened when the performance dept realised their blunder. Suddenly from most of our runways we could still make structural TOW. Ah ha!
Your whole post needs some brain scratching and deep consideration. A quick answer to this question is:
slippery runway adjustments are for performance possibilities not structural weight. You find out what is theoretically the maximum possible and make deductions from that. You may then find that you can still go at max structural. Although 102.8T for B737 does seem fanciful as a start point for 2000m Maybe they have 40k engines.
However, not using max structural weight gives more correct runway performance calculations. This was well demonstrated by one fledgling airline I was with. Their performance dept did just this. The RTOW table topped out at the certified max structural of the fleet. Thus the MTOW dry on a 2500m runway & 3000m runway were the same. When you started making various deductions for go/stop calculations, be it technical or contaminated, you found from a 3000m runway you couldn't make destination fuel, but the local more established airline had no bother. Eyes opened when the performance dept realised their blunder. Suddenly from most of our runways we could still make structural TOW. Ah ha!
