Question: Why is the cruise section there's a slope that looks like climb but no detail is given?
Answer: The Cruise portion of the flight allows for ‘step climbs’ if the airplane benefits for doing so.
Explanation: At altitudes typical of commercial transports, most regions of the world separate east west and west to east to different altitudes. Recently, this separation is now 1000’ for aircraft appropriately equipped (formerly 2000’ – this tightening has been called RVSM – reduced vertical separation minimum). For example, flying a heading from 0 degrees to 179 degrees, aircraft are restricted to 33,000’, 35,000’, 37,000’ etc. From 180 degrees to 359 degrees, to 34,000’, 36,000’, 38,000’ etc. Flying at a constant altitude may not be the most efficient, and it is common practice that once an airplane burns off a certain amount of weight (in fuel), it may be better to climb up 2000’ to the next airway (assuming air traffic control approves…). Whether an airplane does this at all, or does more than one step, varies with the airplane, the mission. This RFP gives the option to do so, if that results in a more efficient airplane. However, a continuous cruise climb (gradually climbing as one cruises along) is not allowed.
Question: On the sixth section for the mission, there is only written climb. was it suppose to climb with 250knt speed?
Answer: Above 10,000’, the climb should be at whatever speed is the most efficient to climb at.
Explanation: Below 10,000’ there is an air traffic control ‘speed limit’ that is practiced in the United States. Aircraft are not to exceed this speed. Once above this altitude, the most optimal climb speed can be used.
Thursday, November 13, 2008
Question: Is an additional 5% of the total flight fuel in addition to fuel for the reserve mission required or is the 5% fuel for the reserve mission?
Answer: the 5% reserve fuel is 5% of the Fuel burn estimated to perform the basic mission….it does not include taxi out fuel, nor taxi in fuel. It does not include the reserve alternate mission profile (200 nm alternate).
Explanation: This portion of the reserve is intended to cover non ideal conditions that might typically occur during a flight. For example, ATC might ask for a non ideal routing (to avoid bad weather, other traffic, etc.). Or headwinds might be worse than forecast. That sort of thing. It does not include the diversion/alternate portion.
Question: Is the 30 min hold at 1500 ft a loiter time?
Answer: The 30 minute hold at 1500’ is simply that. You can call it a loiter. It is also called ‘approach hold’… so it is typically in a configuration and at speeds that would be associated with approach phase of flight.
Explanation: This one is pretty straightforward…..often, aircraft must ‘wait their turn’, either for the weather conditions to improve, or for other traffic to get in ahead….so this ‘hold’ covers the contingency that one might not be able to land immediately at the alternate, or that there was some hesitation before deciding to go the alternate. It is at what would be considered to be more of a ‘pattern altitude’.
Question: Should the two 5 min approach and land times be considered as 5 minute loiters?
Answer: The 5 minute approach and land times…. Should be an estimation of the fuel burn, over the distance traveled at the appropriate speed for the airplane for that phase of the flight.
Explanation: This is simply meant to cover what an airplane would be expected to burn in fuel, and distance traveled (these phases count towards your still air range). Once leveling off at 1500’, the airplane will typically hold, and then be allowed to continue to descent and land. Continuous descents are not yet normal…so this stair stepping is more the norm. The 5 minutes is just to give you the total window for this phase. A 3 degree descent rate is common, (glide slope for instrument approaches), so following that, at whatever speed your airplane is optimized to land at (V approach) from 1500’ will take a couple minutes, ….assume the difference between whatever that number is and 5 minutes, to be the time spent at pattern altitude. I do not consider these to be ‘loiter’….an airplane in descent does not typically burn the same fuel as one maintaining a constant altitude. Also, the constant altitude portion is in the normal landing flap conditions as required of the airplane at that phase (no cleaning up for best endurance loiter …. Although final flaps may not yet be set…).
Question: Initial Cruise Altitude Capability at MTOW: > 35,000’ ISA + 15 C degrees is this altitude and temperature correct?
Answer: As per the initial cruise altitude capability question…yes that is the altitude in feet, with temperature in Celsius above standard day for that altitude.
Explanation: It is a ‘capability’ however. If an aircraft actually wants to optimize out a bit higher of lower when actually flying it’s mission profile, then that is O.K., as long as the airplane can get to 35,000’ if the pilot desires to (is not climb limited, or Buffet limited….).
Answer: the 5% reserve fuel is 5% of the Fuel burn estimated to perform the basic mission….it does not include taxi out fuel, nor taxi in fuel. It does not include the reserve alternate mission profile (200 nm alternate).
Explanation: This portion of the reserve is intended to cover non ideal conditions that might typically occur during a flight. For example, ATC might ask for a non ideal routing (to avoid bad weather, other traffic, etc.). Or headwinds might be worse than forecast. That sort of thing. It does not include the diversion/alternate portion.
Question: Is the 30 min hold at 1500 ft a loiter time?
Answer: The 30 minute hold at 1500’ is simply that. You can call it a loiter. It is also called ‘approach hold’… so it is typically in a configuration and at speeds that would be associated with approach phase of flight.
Explanation: This one is pretty straightforward…..often, aircraft must ‘wait their turn’, either for the weather conditions to improve, or for other traffic to get in ahead….so this ‘hold’ covers the contingency that one might not be able to land immediately at the alternate, or that there was some hesitation before deciding to go the alternate. It is at what would be considered to be more of a ‘pattern altitude’.
Question: Should the two 5 min approach and land times be considered as 5 minute loiters?
Answer: The 5 minute approach and land times…. Should be an estimation of the fuel burn, over the distance traveled at the appropriate speed for the airplane for that phase of the flight.
Explanation: This is simply meant to cover what an airplane would be expected to burn in fuel, and distance traveled (these phases count towards your still air range). Once leveling off at 1500’, the airplane will typically hold, and then be allowed to continue to descent and land. Continuous descents are not yet normal…so this stair stepping is more the norm. The 5 minutes is just to give you the total window for this phase. A 3 degree descent rate is common, (glide slope for instrument approaches), so following that, at whatever speed your airplane is optimized to land at (V approach) from 1500’ will take a couple minutes, ….assume the difference between whatever that number is and 5 minutes, to be the time spent at pattern altitude. I do not consider these to be ‘loiter’….an airplane in descent does not typically burn the same fuel as one maintaining a constant altitude. Also, the constant altitude portion is in the normal landing flap conditions as required of the airplane at that phase (no cleaning up for best endurance loiter …. Although final flaps may not yet be set…).
Question: Initial Cruise Altitude Capability at MTOW: > 35,000’ ISA + 15 C degrees is this altitude and temperature correct?
Answer: As per the initial cruise altitude capability question…yes that is the altitude in feet, with temperature in Celsius above standard day for that altitude.
Explanation: It is a ‘capability’ however. If an aircraft actually wants to optimize out a bit higher of lower when actually flying it’s mission profile, then that is O.K., as long as the airplane can get to 35,000’ if the pilot desires to (is not climb limited, or Buffet limited….).
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