FAR Question

SkyHog

SkyHog

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Everything Offends Me
Last night, at 4am, Richard, KennyFlys, and myself were doing the "find the stupidest or strangest reg" thing. Richard wins. Anyone see this before, and if you have, can you explain why the FAA would require this:

91.126 (c) Flap settings.Except when necessary for training or certification, the pilot in command of a civil turbojet-powered aircraft must use, as a final flap setting, the minimum certificated landing flap setting set forth in the approved performance information in the Airplane Flight Manual for the applicable conditions. However, each pilot in command has the final authority and responsibility for the safe operation of the pilot's airplane, and may use a different flap setting for that airplane if the pilot determines that it is necessary in the interest of safety.
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Here's the debate. Richard says it ensures that you wind up landing at the slowest speed possible. Kenny says it keeps turbojets from landing too fast until they are ensured landing. I say it keeps you going fast and landing no flaps in most GA aircraft, since most POHs or AFMs do not prohibit 0-Flap landings.

1) Why is this a reg? and 2) Which does it require, all of your flaps or none of your flaps on most GA aircraft?

edit: 3) Why is this only required for Class G operations?
 
That is NOT what I said... goodgriefgollygeewhiz! :no:

I said it was to keep the aircraft in a configuration so you are ready to go around and climb. If landing is not assured, particularly in an instrument approach, you wanna climb the most efficient you can. Full or nearly full flaps are going to bite into that performance.

During this discussion I threw a question out there which came from my CFII...

"What's the purpose of a landing?"

I'm gonna leave that hanging while I'm entertained by the answers. :rofl:
 
goodgriefgollygeewhiz, it's not what i said either. I said I think it's a speed restriction (Vfe). For why? I dunno.

EDIT: I will not confirm or deny I was on chat at 4 am. I have no further comment.
 
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SkyHog said:
Last night, at 4am, Richard, KennyFlys, and myself were doing the "find the stupidest or strangest reg" thing. Richard wins. Anyone see this before, and if you have, can you explain why the FAA would require this:



Here's the debate. Richard says it ensures that you wind up landing at the slowest speed possible. Kenny says it keeps turbojets from landing too fast until they are ensured landing. I say it keeps you going fast and landing no flaps in most GA aircraft, since most POHs or AFMs do not prohibit 0-Flap landings.

1) Why is this a reg? and 2) Which does it require, all of your flaps or none of your flaps on most GA aircraft?

edit: 3) Why is this only required for Class G operations?
Click to expand...

Why do you think it only applies to class G? I see it as only applying to turbojets under part 91.

One could argue that it's there to prohibit:
a. turbojets landing with too little flaps (and thus too much energy)
b. turbojets landing with too much flaps (and thus not enough energy for a go-around).

In my experience with today's turbojets under part 91, the problem is NOT a lack of thrust for go-around.

And it doesn't affect most GA aircraft at all, as it only applies to the jets.
 
IMO this FAR is poorly worded and is really meant to insure that at least the minimum flap setting is used rather than to limit flap deployment to the minimum in the POH.

And I hope everyone realizes this only applies to turbojets, not turboprops or piston powered airplanes.
 
It's a noise rule -- more flap = more drag = more thrust required = more noise. They want jets to use the least flap feasible in order to minimize noise.
 
KennyFlys said:
That is NOT what I said... goodgriefgollygeewhiz! :no:



During this discussion I threw a question out there which came from my CFII...

"What's the purpose of a landing?"

I'm gonna leave that hanging while I'm entertained by the answers. :rofl:
Click to expand...

The purpose of a non-emergency landing in an aircraft is to ensure the possibility of an immediate future takeoff, by that pilot, in that aircraft.
 
TMetzinger said:
Why do you think it only applies to class G? I see it as only applying to turbojets under part 91.
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Sorry, should have pointed that out. The section is titled "Class G Operations."

So it appears everyone here is torn about its meaning too. We have almost a 50/50 split about whether jets have to use at least the minimum flap setting, or the minimum flap setting. Weird.
 
ive always thought it was the thurman munson reg too. i always thought it was so to lower the stall speed on approach, which thurman may have appreciated.
 
When an aircraft, especially a transport category aircraft, is certificated, the builder is required by the certifying authority to provide the eventual operator of the airplane with very comprehensive performance data for all the phases of flight. That is the builders burden. Our burden as pilots is to ensure that we use that "approved performance information in the AFM" to operate the aircraft as it was intended to be operated lest the outcome be in doubt. So when Raytheon gives us a 130 knot vref with flaps 25 to a dry runway that will take us 4400 feet to stop, we have some assurance that if we use the book numbers we get book performance. The passengers like that!
 
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Dave Krall CFII said:
The purpose of a non-emergency landing in an aircraft is to ensure the possibility of an immediate future takeoff, by that pilot, in that aircraft.
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Yep, if you force it down the force indeed will NOT be with you and it will likely be your last landing. I'm surprised there was only one jab at an answer.

At least I was pretty close on my jab at the original question. You want to maintain speed, control and ability to get out of a situation should things deteriorate. I had not ever read the Munson report. There are too many more recent reports being made to get time to dig back into history!
 
Ron Levy said:
It's a noise rule -- more flap = more drag = more thrust required = more noise. They want jets to use the least flap feasible in order to minimize noise.
Click to expand...

Makes sense if you were talking about takeoffs, but landings, even in jets, aren't conducted at high power settings, and for the 737 at least, power settings (and therefore noise) don't vary much with flap settings - you pretty much use the same power and get different Vref speeds.

Got any discussion or something else to cite for your comment? It makes as much sense as anything else, but doesn't seem MORE likely than targeting it at landing ops (as Eamon seems to believe).
 
I'm not going to comment on the wording of that reg and I've only flown 3 different models of turbojet airplanes, but in all of them I was taught to always land with full flaps unless there is something abnormal going on. I think I've only landed with less than full flaps in a real airplane 2 or 3 times and that was simulating an engine out landing in an airplane where the procedure is to use 20 flaps (instead of 40) for a single engine landing. We practice flaps up landings in the sim but I've never done one in the real deal.

As far as noise goes, some noise abatement landing procedures call for delaying full flaps as late as possible because of the extra power you need to overcome the drag.
 
TMetzinger said:
Makes sense if you were talking about takeoffs, but landings, even in jets, aren't conducted at high power settings, and for the 737 at least, power settings (and therefore noise) don't vary much with flap settings - you pretty much use the same power and get different Vref speeds.

Got any discussion or something else to cite for your comment? It makes as much sense as anything else, but doesn't seem MORE likely than targeting it at landing ops (as Eamon seems to believe).
Click to expand...

What powere setting would it be for a go-around at 50' agl w/ flaps set to min vs. full flaps for a 737?
 
Landings in the 737/738/739 (the ones I'm studying) are normally performed with flaps 30 or 40 settings, dependent on conditions.

The rejected landing procedure at the carrier who I'm studying is...

Set thrust by clicking the TOGA button once, or (if no autothrottles), push the thrust levers full forward - the ECUs will prevent exceedances), rotate to 15 degrees pitch up, and call for flaps 15.
At positive rate of climb, call for the gear.
Climb out at V2+15 until 1000 AGL, then set flaps 5, pitch for 250 KIAS, set climb power, and retract flaps on schedule.

Now, the NG737s use relatively high bypass fans, so they may not be the target of the noise concerns here. Perhaps more importantly, there's nothing in my ops manual about noise concerns for a rejected landing or missed approach until the airplane is 1000 AGL and resuming a "normal" takeoff/climb profile. Some specific airports may alter these procedures, but even then, the usual noise abatement profile doesn't call for reduced thrust, it usually calls for a steeper climb to a minimum altitude and then a reduction in power, so that your noise footprint stays inside a specific area. One of the mags recently described a SWA departure procedure for a noise sensitive california airport, and I think the climb attitude was 20-25 instead of the more normal 15-20, but takeoff power wasn't reduced.

Normal flap settings for takeoff are 5, 10, or 15 degrees based on conditions, with occasional settings of 25 degrees (Midway when heavy comes to mind).

Best wishes,
 
Ron Levy said:
It's a noise rule -- more flap = more drag = more thrust required = more noise. They want jets to use the least flap feasible in order to minimize noise.
Click to expand...

I could be wrong, but I can't imagine that the FAA would require what is essentially a less safe procedure to lessen the noise impact of landing jets generically. Many of the class G airports that this would apply to are far enough into the boonies that only the cows would care.
 
It doesn't just apply to Class G airspace (91.126). Notice in 91.127 Class E airspace requires "each person operating an aircraft on or in the vicinity of an airport in a Class E airspace area must comply with the requirements of §91.126." Now look at 91.128 Class D airspace which reads "each person operating an aircraft in Class D airspace must comply with the applicable provisions of this section. In addition, each person must comply with §§91.126 and 91.127."

The requirement is carried forward into successively more complex airspace.
 
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