A Surprising $5000 Error
5 months 2 days ago - 5 months 2 days ago #17764
by Westcoast
A Surprising $5000 Error was created by Westcoast
Most of my flying these days has been for my regional airline (Aklak Air) using "Econ Mode" and operating out of the Minneapolis Hub If you've tried the Econ flights you know that the objective is to run a profitable regional airline under (sort of, kinda) real world conditions. So this means selecting one of the posted available Hub flights and executing it in the available time while maximizing your margin by minimizing the costs of your flight while carrying the assigned payload and executing the flight skillfully so as not to incur penalties by roughing up the passengers in turbulent air or setting your aircraft down too hard, or by arriving without sufficient reserve fuel. So all of these things are monitored during you flight and you get a score at the end expressed as a positive or negative profit margin which then gets added to you cumulative profit. I like these flights for several reasons, but principally because they seem more challenging to me that flying the regular flights on our various hub schedules. Up to this point, my major problem has been hard landings, for which I am frequently "docked". I can explain this problem, but I'll let that wait for another post.
Anyhow, having been the author of the (very simple) computational "engine" behind our Econ 2018 model, I know what is required to be consistently profitable. The key is to fit the aircraft to the assignment, and then to execute the flight skillfully, using just enough fuel to have the required reserve on landing. You get to choose any aircraft in your "hangar" to execute these flights, but the key is to match the aircraft to the assigned flight. The most important thing is to get your aircraft as close to full as possible without exceeding any of the constraints (MTOW, etc.) That's because your costs go up with aircraft MTOW and your revenue goes up with increasing passenger/cargo load.
So, today I choose Econ flight number 610232 from Lexington, KY. to Minneapolis, carrying 99 passengers and 4,950 pounds of cargo. Fortunately, this just fits the largest aircraft in the Aklak Air hangar, a Bombardier CRJ-1000, which seats a maximum of 104 in single class service (we are a budget airline, no business or first class, no free meals or alcohol) - sorry. That's how we make so much money; just a little less than Rogers Air which is run by the President of SPA, so of course the competition is fixed .
So today I filed my request for flight 610232 just before requesting my clearance and permission to "Push and Start". Things looked good. I was carrying the requisite passenger load of 99 and cargo of 4950. Using Simbrief to plan the flight, I had 11,940 lbs of jet fuel. That's 2000 lbs more than the "block fuel" load computed by Simbrief, because, I have found that I consistently use a little more fuel than predicted, probably because I alway descend right away when ATC gives me a "pilot discretion" to FL XXX, in order not to get ragged on by FSDO for busting my altitude constraints. Hence, I fly lower longer and burn a little more fuel. Never-the-less, the numbers looked good, a TOW of 82659 lbs, vs. a MTOW of 91,800 lbs. That suggested that I shouldn't have much difficulty in quickly getting to my ATC assigned altitude of FL320. If I am close to the MTOW on takeoff, I have to watch carefully not to stall the aircraft as I approach the assigned altitude with a near full fuel load Finally, Lexington is a regional airport and the longest runway is only 7004' long. But my spec sheet says the takeoff distance for a CRC1000 at MTOW is 6821 ft. and I was starting at only 90% of MTOW, so it should be a little close, but well within company and FAR requirements. I alway check this stuff out before I contract for the flight, because, if for any reason I fail to execute the flight within the assigned time, I will have to pay a $5000 penalty. Ouch! That's an appreciable fraction of the average profit I make on a completed flight. So, I don't want this to happen.. Anyhow, everything looked good: Rwy 22 (7004 ft.) with with a little head/cross wind 270/5, so I went ahead and reserved the flight.
Before I asked for my clearance, it occurred to me that Navigraph has just announced a new feature in it's software suite supporting the Simbrief tool: computation of takeoff and landing performance. I have been looking for that, because my aircraft models do not provide that into. So, I decided to use the new tool to make the Takeoff performance calculation. Since it's embedded in simbrief, the required input data fields were already populated with all of the required data, TOW (82659 lbs), Rwy length (7004 ft.), wind (270/4), and temperature (24 C). The module expresses it's output in a single number - "Maximum Runway Weight". For my flight that number was 80,715 lbs. DRAT! This means I'll have to ask (82659 - 80715)/170 = 11.4 of my passengers to disembark before takeoff in order not to bust the limit. That also means I'll have to offer them money or flight credits to get them off the plane. On top of that, I won't make any money on this flight. Best to send everybody home and eat the $5000..
So, what went wrong? Fortunately, the tool allows me to make the calculation with different input parameters. If the temperature were 10 C (50 F), instead of 24 C (75 F) the air would be denser and thus provide more lift, and the tool says "Solution provided with bleeds off". Likewise, were the wind 270/22, I could take off because the takeoff roll would begin with a higher airspeed (A/C speed relative to the air).
Maybe the model is wrong! I'm going to deplane he passengers and replace them with 170 lb. sandbags, just to see. If we crash, we'll be looking for investors to help us built back the Aklak fleet, but I'll no longer be the CEO.
- Always more than you wanted to know.
Mike
P.S. After a rather long ATC hold (dinner), the temperature dropped a little and I managed to get off with maybe 300 ft. of runway remaining at rotation. Flight otherwise went well.
Anyhow, having been the author of the (very simple) computational "engine" behind our Econ 2018 model, I know what is required to be consistently profitable. The key is to fit the aircraft to the assignment, and then to execute the flight skillfully, using just enough fuel to have the required reserve on landing. You get to choose any aircraft in your "hangar" to execute these flights, but the key is to match the aircraft to the assigned flight. The most important thing is to get your aircraft as close to full as possible without exceeding any of the constraints (MTOW, etc.) That's because your costs go up with aircraft MTOW and your revenue goes up with increasing passenger/cargo load.
So, today I choose Econ flight number 610232 from Lexington, KY. to Minneapolis, carrying 99 passengers and 4,950 pounds of cargo. Fortunately, this just fits the largest aircraft in the Aklak Air hangar, a Bombardier CRJ-1000, which seats a maximum of 104 in single class service (we are a budget airline, no business or first class, no free meals or alcohol) - sorry. That's how we make so much money; just a little less than Rogers Air which is run by the President of SPA, so of course the competition is fixed .
So today I filed my request for flight 610232 just before requesting my clearance and permission to "Push and Start". Things looked good. I was carrying the requisite passenger load of 99 and cargo of 4950. Using Simbrief to plan the flight, I had 11,940 lbs of jet fuel. That's 2000 lbs more than the "block fuel" load computed by Simbrief, because, I have found that I consistently use a little more fuel than predicted, probably because I alway descend right away when ATC gives me a "pilot discretion" to FL XXX, in order not to get ragged on by FSDO for busting my altitude constraints. Hence, I fly lower longer and burn a little more fuel. Never-the-less, the numbers looked good, a TOW of 82659 lbs, vs. a MTOW of 91,800 lbs. That suggested that I shouldn't have much difficulty in quickly getting to my ATC assigned altitude of FL320. If I am close to the MTOW on takeoff, I have to watch carefully not to stall the aircraft as I approach the assigned altitude with a near full fuel load Finally, Lexington is a regional airport and the longest runway is only 7004' long. But my spec sheet says the takeoff distance for a CRC1000 at MTOW is 6821 ft. and I was starting at only 90% of MTOW, so it should be a little close, but well within company and FAR requirements. I alway check this stuff out before I contract for the flight, because, if for any reason I fail to execute the flight within the assigned time, I will have to pay a $5000 penalty. Ouch! That's an appreciable fraction of the average profit I make on a completed flight. So, I don't want this to happen.. Anyhow, everything looked good: Rwy 22 (7004 ft.) with with a little head/cross wind 270/5, so I went ahead and reserved the flight.
Before I asked for my clearance, it occurred to me that Navigraph has just announced a new feature in it's software suite supporting the Simbrief tool: computation of takeoff and landing performance. I have been looking for that, because my aircraft models do not provide that into. So, I decided to use the new tool to make the Takeoff performance calculation. Since it's embedded in simbrief, the required input data fields were already populated with all of the required data, TOW (82659 lbs), Rwy length (7004 ft.), wind (270/4), and temperature (24 C). The module expresses it's output in a single number - "Maximum Runway Weight". For my flight that number was 80,715 lbs. DRAT! This means I'll have to ask (82659 - 80715)/170 = 11.4 of my passengers to disembark before takeoff in order not to bust the limit. That also means I'll have to offer them money or flight credits to get them off the plane. On top of that, I won't make any money on this flight. Best to send everybody home and eat the $5000..
So, what went wrong? Fortunately, the tool allows me to make the calculation with different input parameters. If the temperature were 10 C (50 F), instead of 24 C (75 F) the air would be denser and thus provide more lift, and the tool says "Solution provided with bleeds off". Likewise, were the wind 270/22, I could take off because the takeoff roll would begin with a higher airspeed (A/C speed relative to the air).
Maybe the model is wrong! I'm going to deplane he passengers and replace them with 170 lb. sandbags, just to see. If we crash, we'll be looking for investors to help us built back the Aklak fleet, but I'll no longer be the CEO.
- Always more than you wanted to know.
Mike
P.S. After a rather long ATC hold (dinner), the temperature dropped a little and I managed to get off with maybe 300 ft. of runway remaining at rotation. Flight otherwise went well.
Last edit: 5 months 2 days ago by Westcoast. Reason: Information update.
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5 months 2 days ago - 5 months 2 days ago #17765
by jer029
Replied by jer029 on topic A Surprising $5000 Error
Hah Mike,
I would have just taken off with my fingers crossed - figuring that the margin of error would allow that minor overweight takeoff. In the sim it is usually possible, however I have occasionally exceeded the margin of error or the COG with tragic results. This more liberal and higher risk flight planning proves to be financially better for the company, even with the occasional payout for a flight tragedy - not much of a consolation for the families of the passengers on those flights however. Hmm...this Econ Mod might be more realistic than we thought it was...sadly.
Anyway, Aklak Air should have no problem overtaking Rogers Air, as my pilots have been on strike lately. I know we pay well, so perhaps it's the seat-of-the-pants flight planning that stresses them out.
Happy flying,
John
I would have just taken off with my fingers crossed - figuring that the margin of error would allow that minor overweight takeoff. In the sim it is usually possible, however I have occasionally exceeded the margin of error or the COG with tragic results. This more liberal and higher risk flight planning proves to be financially better for the company, even with the occasional payout for a flight tragedy - not much of a consolation for the families of the passengers on those flights however. Hmm...this Econ Mod might be more realistic than we thought it was...sadly.
Anyway, Aklak Air should have no problem overtaking Rogers Air, as my pilots have been on strike lately. I know we pay well, so perhaps it's the seat-of-the-pants flight planning that stresses them out.
Happy flying,
John
Last edit: 5 months 2 days ago by jer029.
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5 months 1 day ago #17766
by Westcoast
Replied by Westcoast on topic A Surprising $5000 Error
John,
If you read the edit on my post, (a P.S. on the bottom), you'll see that I did fly the flight somewhat later, after some change in the weather. Unfortunately, I did not repeat the takeoff performance calculation then to see if I was within the allowable takeoff weight. As it turns out my copilot called out rotate several hundred feet before the end of the runway and I got off safely. That might have been attributable to the dropping outside air temperature or the conservatism/inaccuracy of the performance modeling of my aircraft. One of the problems with these middle grade (i.e. easy to learn) aircraft is that they are of dubious technical validity and don't come with the software necessary to compute flap settings, V speeds, etc.
I have a high quality (and very complicated) Aerosoft A318-321 model which I would like to learn, but those aircraft are in the High Cat IV to Cat V
range and would be of very limited use in flying the ECON flights as they are now set-up.
Mike
If you read the edit on my post, (a P.S. on the bottom), you'll see that I did fly the flight somewhat later, after some change in the weather. Unfortunately, I did not repeat the takeoff performance calculation then to see if I was within the allowable takeoff weight. As it turns out my copilot called out rotate several hundred feet before the end of the runway and I got off safely. That might have been attributable to the dropping outside air temperature or the conservatism/inaccuracy of the performance modeling of my aircraft. One of the problems with these middle grade (i.e. easy to learn) aircraft is that they are of dubious technical validity and don't come with the software necessary to compute flap settings, V speeds, etc.
I have a high quality (and very complicated) Aerosoft A318-321 model which I would like to learn, but those aircraft are in the High Cat IV to Cat V
range and would be of very limited use in flying the ECON flights as they are now set-up.
Mike
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