Is there ever a time when you would climb out flying a DP, and use VNAV and Flight Level Change together?

I use VNAV to climb out and fly the DP with altitude constraints at each waypoint. If I want to climb straight up to what I have set in my altitude select window, I use Flight Level Change.

rfresh737 wrote:

Is there ever a time when you would climb out flying a DP, and use VNAV and Flight Level Change together?

I use VNAV to climb out and fly the DP with altitude constraints at each waypoint. If I want to climb straight up to what I have set in my altitude select window, I use Flight Level Change.

No. VNAV is a combined power setting/navigation tool whereas FLT LVL CHG is strictly a power setting tool. You can use one or the other but not at the same time.

rfresh737 wrote:

Is there ever a time when you would climb out flying a DP, and use VNAV and Flight Level Change together?

I use VNAV to climb out and fly the DP with altitude constraints at each waypoint. If I want to climb straight up to what I have set in my altitude select window, I use Flight Level Change.

If you mean "simultaneously", then no. If you mean in the course of flying the procedure, then sure. It's a tactical decision based on the situation. You might keep it in VNAV (CLB on Airbus) but if, for example, an altitude constraint is waived, you could use FLCH (OP CLB on Airbus).

rfresh737 wrote:

Is there ever a time when you would climb out flying a DP, and use VNAV and Flight Level Change together?

I use VNAV to climb out and fly the DP with altitude constraints at each waypoint. If I want to climb straight up to what I have set in my altitude select window, I use Flight Level Change.

As others said, VNAV and FLCH can not be used at the same time.

FLCH is similar to an IAS mode, in that the aircraft will pitch (and power, it so equipped) for a certain airspeed in climb and maintain that speed, regardless of rate of climb. This is useful when you want to maintain a certain speed for legal or operational reasons and don't need to meet a restriction. VNAV will pitch to meet any programmed restriction, regardless of speed.

Yikes! wrote:

rfresh737 wrote:

Is there ever a time when you would climb out flying a DP, and use VNAV and Flight Level Change together?

I use VNAV to climb out and fly the DP with altitude constraints at each waypoint. If I want to climb straight up to what I have set in my altitude select window, I use Flight Level Change.

No. VNAV is a combined power setting/navigation tool whereas FLT LVL CHG is strictly a power setting tool. You can use one or the other but not at the same time.

Uh, plenty of aircraft with manual thrust have FLCH mode on their autopilot.

In the history of overthought arguments, this is one of them.

Not banging on you or anything, but you use what you need when you need it. Don't nuke it to death.

Need FLC? Use it, pull the knob and announce "Flight Level Change to 230"

Need PROF/VNAV? Spin the knob and watch the magic happen.

N1120A wrote:

FLCH is similar to an IAS mode, in that the aircraft will pitch (and power, it so equipped) for a certain airspeed in climb and maintain that speed, regardless of rate of climb. This is useful when you want to maintain a certain speed for legal or operational reasons and don't need to meet a restriction. VNAV will pitch to meet any programmed restriction, regardless of speed.

Yikes! wrote:

rfresh737 wrote:

Is there ever a time when you would climb out flying a DP, and use VNAV and Flight Level Change together?

I use VNAV to climb out and fly the DP with altitude constraints at each waypoint. If I want to climb straight up to what I have set in my altitude select window, I use Flight Level Change.

No. VNAV is a combined power setting/navigation tool whereas FLT LVL CHG is strictly a power setting tool. You can use one or the other but not at the same time.

Uh, plenty of aircraft with manual thrust have FLCH mode on their autopilot.

Is there any actual difference in capabilities between between modes labeled as IAS and FLCH? Or is it just a difference in labeling? I’m not a pilot but do flight sims pretty regularly and I always assumed it was the latter.

As for your second point, this is true. Both the SF-50 and the CRJ-200 have FLC modes yet neither has auto throttle .

BowlingShoeDC9 wrote:

N1120A wrote:

FLCH is similar to an IAS mode, in that the aircraft will pitch (and power, it so equipped) for a certain airspeed in climb and maintain that speed, regardless of rate of climb. This is useful when you want to maintain a certain speed for legal or operational reasons and don't need to meet a restriction. VNAV will pitch to meet any programmed restriction, regardless of speed.

Yikes! wrote:

No. VNAV is a combined power setting/navigation tool whereas FLT LVL CHG is strictly a power setting tool. You can use one or the other but not at the same time.

Uh, plenty of aircraft with manual thrust have FLCH mode on their autopilot.

Is there any actual difference in capabilities between between modes labeled as IAS and FLCH? Or is it just a difference in labeling? I’m not a pilot but do flight sims pretty regularly and I always assumed it was the latter.

As for your second point, this is true. Both the SF-50 and the CRJ-200 have FLC modes yet neither has auto throttle .

Yes. IAS just maintains speed. FLCH maintains speed at a given power setting and adjusts pitch accordingly to maintain that speed. As the name implies, only used when changing altitudes.

AirKevin wrote:

BowlingShoeDC9 wrote:

N1120A wrote:

FLCH is similar to an IAS mode, in that the aircraft will pitch (and power, it so equipped) for a certain airspeed in climb and maintain that speed, regardless of rate of climb. This is useful when you want to maintain a certain speed for legal or operational reasons and don't need to meet a restriction. VNAV will pitch to meet any programmed restriction, regardless of speed.



Uh, plenty of aircraft with manual thrust have FLCH mode on their autopilot.

Is there any actual difference in capabilities between between modes labeled as IAS and FLCH? Or is it just a difference in labeling? I’m not a pilot but do flight sims pretty regularly and I always assumed it was the latter.

As for your second point, this is true. Both the SF-50 and the CRJ-200 have FLC modes yet neither has auto throttle .

Yes. IAS just maintains speed. FLCH maintains speed at a given power setting and adjusts pitch accordingly to maintain that speed. As the name implies, only used when changing altitudes.

I think we may be talking about different things. In some aircraft, such as the Beechcraft King Air C90 (or at least the one modeled in Xplane 11 does) there is a mode called IAS which appears to adjust pitch to maintain the speed the aircraft was going when you turned on the mode. Similarly, there is an auto pilot mode for the CR2 which is labeled “Speed” that does the same thing as “IAS” on the C90. I wasn’t sure if there were any additional capabilities that aircraft with FLC modes had or if it was just a labeling choice decided by the manufacturer.

BowlingShoeDC9 wrote:

AirKevin wrote:

BowlingShoeDC9 wrote:

Is there any actual difference in capabilities between between modes labeled as IAS and FLCH? Or is it just a difference in labeling? I’m not a pilot but do flight sims pretty regularly and I always assumed it was the latter.

As for your second point, this is true. Both the SF-50 and the CRJ-200 have FLC modes yet neither has auto throttle .

Yes. IAS just maintains speed. FLCH maintains speed at a given power setting and adjusts pitch accordingly to maintain that speed. As the name implies, only used when changing altitudes.

I think we may be talking about different things. In some aircraft, such as the Beechcraft King Air C90 (or at least the one modeled in Xplane 11 does) there is a mode called IAS which appears to adjust pitch to maintain the speed the aircraft was going when you turned on the mode. Similarly, there is an auto pilot mode for the CR2 which is labeled “Speed” that does the same thing as “IAS” on the C90. I wasn’t sure if there were any additional capabilities that aircraft with FLC modes had or if it was just a labeling choice decided by the manufacturer.

In that case, that's just confusing. IAS can be used when changing altitudes or level. FLCH can only be used when changing altitudes. To have them both do the same thing just sounds very confusing, and I am quite befuddled.

AirKevin wrote:

BowlingShoeDC9 wrote:

AirKevin wrote:

Yes. IAS just maintains speed. FLCH maintains speed at a given power setting and adjusts pitch accordingly to maintain that speed. As the name implies, only used when changing altitudes.

I think we may be talking about different things. In some aircraft, such as the Beechcraft King Air C90 (or at least the one modeled in Xplane 11 does) there is a mode called IAS which appears to adjust pitch to maintain the speed the aircraft was going when you turned on the mode. Similarly, there is an auto pilot mode for the CR2 which is labeled “Speed” that does the same thing as “IAS” on the C90. I wasn’t sure if there were any additional capabilities that aircraft with FLC modes had or if it was just a labeling choice decided by the manufacturer.

In that case, that's just confusing. IAS can be used when changing altitudes or level. FLCH can only be used when changing altitudes. To have them both do the same thing just sounds very confusing, and I am quite befuddled.

To clarify, in those planes there is no FLC mode. The IAS mode serves the same purpose. Neither the C90 or the CR2 (at least the ones in XPlane) have auto throttle so there isn't any speed keep abilities other than you working the throttle.

XPlane is not a real airplane. In real airplanes, autothrottles are now available in a King Air, including a C90. They are not in a CRJ-200.

FLCH assumes enough excess power to climb. IAS doesn't make that assumption. In general, however, those modes function similarly and are there to provide both over and under speed protection.

I use VFLC practically every climb in an aircraft with no autothrottles. Set a power setting and leave the thrust levers alone.


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N1120A wrote:

XPlane is not a real airplane. In real airplanes, autothrottles are now available in a King Air, including a C90. They are not in a CRJ-200.

FLCH assumes enough excess power to climb. IAS doesn't make that assumption. In general, however, those modes function similarly and are there to provide both over and under speed protection.

For what it's worth, in a CRJ, there are 3 modes that can be done with the "SPEED" button on the FCP. You can get Climb, Descend, or IAS modes. Climb will pitch to maintain the selected airspeed in a climb, doing no less than 50FPM in the climb. Descend is the same way, no less than 50FPM descending. IAS mode will pitch to maintain the airspeed selected, with no protection of it being a climb or descent.

So i fly a couple different kind of business jets. We never use VNAV in the climb, very few departures have altitudes that we need to stop at or be under so we will use FLC or VS in the climb exclusively. Just set the power and climb, if there is a restriction we need to make we will just do it manually.

qcpilotxf wrote:

So i fly a couple different kind of business jets. We never use VNAV in the climb, very few departures have altitudes that we need to stop at or be under so we will use FLC or VS in the climb exclusively. Just set the power and climb, if there is a restriction we need to make we will just do it manually.

Just beware that further along in your career you will encounter departure procedures that do have nav/alt restrictions embedded. Hence VNAV vs strict FLT CH/HDG SEL.

Yikes! wrote:

qcpilotxf wrote:

So i fly a couple different kind of business jets. We never use VNAV in the climb, very few departures have altitudes that we need to stop at or be under so we will use FLC or VS in the climb exclusively. Just set the power and climb, if there is a restriction we need to make we will just do it manually.

Just beware that further along in your career you will encounter departure procedures that do have nav/alt restrictions embedded. Hence VNAV vs strict FLT CH/HDG SEL.

We regularly fly in and out of a couple airports that have restrictions on departures, it is normally just a briefing item for us and we handle them the old school way rather than letting our (rather unreliable) box calculate the profile for us. While business jet avionics have come a long way, those of us flying older ones (10-20 years +) are still years behind the modern avionics in new business jets or even in the airliners of the time our jets were built.

These comments are based on 737 vnav but other aircraft are similar. Much of the time, the vnav functions identically to level change. During periods of unrestricted climb, vnav speed is max climb thrust, speed bug as set by the fmc. Only to meet a restriction does it enter a path mode. Similarly in the descent, once it enters its calculated idle path to meet the first descent restriction, using idle thrust and speed bug as set by the fmc, it is functionally in the same as a level change descent…. Except for the ability to honor restrictions other than the altitude window.

N1120A wrote:

XPlane is not a real airplane. In real airplanes, autothrottles are now available in a King Air, including a C90. They are not in a CRJ-200.

FLCH assumes enough excess power to climb. IAS doesn't make that assumption. In general, however, those modes function similarly and are there to provide both over and under speed protection.

Thank you for the explanation of the subtle difference between the two modes. I figured there had to be some slight difference between FLC and IAS modes.