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SWA GUY
BMF
- Joined
- Apr 27, 2002
- Posts
- 627
At SWA, in all but the -200, we fly box speeds for the climb outta 10,000. Due to a headwind or tailwind, the box will project the most fuel efficient speed. The speeds can range, generally, from about 275 to 315 depending on the situation.
If we level off prior to the Flight Levels, on the climb side, we fly 300kts or .72M whichever is lower.
In cruise, and in the Flight Levels, we fly what the box says to fly, unless of course ATC or turbulence is a factor.
In the descent, we fly what the box says to fly, normally your cruise speed until the transition. Then its usually 280kts. If we level off, between the Flight Levels and 10,000, we fly 280kts.
That's what the book says at least....Although I've never seen anything different, I've HEARD some people fly a little bit faster than that.
If we level off prior to the Flight Levels, on the climb side, we fly 300kts or .72M whichever is lower.
In cruise, and in the Flight Levels, we fly what the box says to fly, unless of course ATC or turbulence is a factor.
In the descent, we fly what the box says to fly, normally your cruise speed until the transition. Then its usually 280kts. If we level off, between the Flight Levels and 10,000, we fly 280kts.
That's what the book says at least....Although I've never seen anything different, I've HEARD some people fly a little bit faster than that.
MLBWINGBORN
Freedom Fighter
- Joined
- Nov 27, 2001
- Posts
- 476
justApilot
Dawn Patroller
- Joined
- Jan 27, 2002
- Posts
- 346
Dr. Hootie
Member
- Joined
- Sep 12, 2002
- Posts
- 10
It's all about costs
In the FMC, you type in a cost index (i.e., a number which has meaning to the bean counters). Usually your airline will have a favorite figure. Then the box (FMC) figures out your optimum speeds based on your weight, temps, cruise altitude, etc., given the cost index that you input. This helps optimize the airplane's performance vs. fuel burn during the flight.
So you typically fly the speeds that "the box" says. If you deviate too much from it, you may burn more fuel than the company would like.....not a good thing.
In the FMC, you type in a cost index (i.e., a number which has meaning to the bean counters). Usually your airline will have a favorite figure. Then the box (FMC) figures out your optimum speeds based on your weight, temps, cruise altitude, etc., given the cost index that you input. This helps optimize the airplane's performance vs. fuel burn during the flight.
So you typically fly the speeds that "the box" says. If you deviate too much from it, you may burn more fuel than the company would like.....not a good thing.
justApilot
Dawn Patroller
- Joined
- Jan 27, 2002
- Posts
- 346
Cost Index of 28 in -300/-500, or 36 in a -700.
Of course, if you get an "expect holding at ___, airspeed your discretion" on the way in to, say, STL, you can change the cost index to a 0 & you'll get max economy speed (since you might as well get to your holding fix as efficiently as possible).
Or, if you get a request for "max forward airspeed," put in a cost index of 200 & the box will automatically figure your arrival fuel & descent profiles & such around that parameter. Mike's technique gets used in that situation as well (or so I've heard).
Cheers!
Of course, if you get an "expect holding at ___, airspeed your discretion" on the way in to, say, STL, you can change the cost index to a 0 & you'll get max economy speed (since you might as well get to your holding fix as efficiently as possible).
Or, if you get a request for "max forward airspeed," put in a cost index of 200 & the box will automatically figure your arrival fuel & descent profiles & such around that parameter. Mike's technique gets used in that situation as well (or so I've heard).
Cheers!
ON the 717-200, we use a Cost index of 30, and then use box speeds for the majority of the profile- from t/o until in the close in approach phase. Typically this will give us climb speeds of between 288 and 311 kias, for the climb, with crossover at between .765 and .779. Descents usually are right at 300 kias.
)
chperplt
Registered User
- Joined
- Nov 25, 2001
- Posts
- 4,123
On the Beech 1900, we use the posterior index to figure out power settings. You take the enroute time in minutes and multiply it by how much you've had to drink in liters, then divide by 1.0 if you are going to be underblock for the month, or 1.5 if you are overblock. The resultant percentage is your % torque to be used.
DC-9
The company book says climb and descend at 280kts and long range cruise .73-.76M (We don't got no fancy 'box' in them there planes.)
Most guys go up and down at 300-330 and cruise at .78-80Mach and will under-burn the computer by 500-1000lbs per leg.
CLIMB: Sometimes aero equations are no match for pilot experience. L/Dmax is approx. Weight + 100 = kts. So this implies slower is more efficient, but I say BS. At the 10,000' acceleration it only takes another minute climbing at 1000fpm to go from 280 to 320 kts. Fuel flow will be the same b/c you're at climb power. The difference comes in at the glass wall that starts between 17,000 and FL220. {This is especially true on -7 or -11 engines and is even worse on a hot day.} The climb rate will be 200-400 fpm higher at 320 versus 280 and you have been going faster during the whole climb at the same burn rate. Inertia.
DESCEND: At first glance it makes sense to go to flight idle nice and early and stroll down at 280 kts. OR you could stay at altitude for an extra 2-3 minutes and descend at 300-330 (or clacker) to 25-30nm from the field. It only cost you another 2 minutes at cruise but again you are going faster so you will be in the air less time (ie less burn). If you fly the book profile and are off or get a short vector, you are now burning a lot of gas down low. Having the extra smash buys a little more time for deviations. And even if you tend to be a little high and have dirty up at little earlier than optimum. On average you will save gas because you are spooling up the motors at 1000AGL rather than 30 miles ago.
Take all this with a grain of salt because:
1. The DC-9 can get down in a hurry if you need it to
2. I fly boxes so customer comfort is not a factor
3. I fly at night so Center is less likely to say lose 12000ft in 3 minutes, maintain 250 kts.
4. I have a type A personality and get too many speeding tickets
The company book says climb and descend at 280kts and long range cruise .73-.76M (We don't got no fancy 'box' in them there planes.)
Most guys go up and down at 300-330 and cruise at .78-80Mach and will under-burn the computer by 500-1000lbs per leg.
CLIMB: Sometimes aero equations are no match for pilot experience. L/Dmax is approx. Weight + 100 = kts. So this implies slower is more efficient, but I say BS. At the 10,000' acceleration it only takes another minute climbing at 1000fpm to go from 280 to 320 kts. Fuel flow will be the same b/c you're at climb power. The difference comes in at the glass wall that starts between 17,000 and FL220. {This is especially true on -7 or -11 engines and is even worse on a hot day.} The climb rate will be 200-400 fpm higher at 320 versus 280 and you have been going faster during the whole climb at the same burn rate. Inertia.
DESCEND: At first glance it makes sense to go to flight idle nice and early and stroll down at 280 kts. OR you could stay at altitude for an extra 2-3 minutes and descend at 300-330 (or clacker) to 25-30nm from the field. It only cost you another 2 minutes at cruise but again you are going faster so you will be in the air less time (ie less burn). If you fly the book profile and are off or get a short vector, you are now burning a lot of gas down low. Having the extra smash buys a little more time for deviations. And even if you tend to be a little high and have dirty up at little earlier than optimum. On average you will save gas because you are spooling up the motors at 1000AGL rather than 30 miles ago.
Take all this with a grain of salt because:
1. The DC-9 can get down in a hurry if you need it to
2. I fly boxes so customer comfort is not a factor
3. I fly at night so Center is less likely to say lose 12000ft in 3 minutes, maintain 250 kts.
4. I have a type A personality and get too many speeding tickets
justApilot
Dawn Patroller
- Joined
- Jan 27, 2002
- Posts
- 346
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