Manifold Pressure Gauge

Chuck Dillon

Filing Flight Plan
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grnbrt1956
Okay porably a real stupid question here, I went out to practice for my CFI checkride the other day. Climbed in the FBO Arrow preflight, taxi and runup all okay.

Just after takeoff at about 400' I looked down MP shows 12" ! Okay oil presure okay, oil temp okay mmmmm I elected to do an immediate return, land, taxi off full power run up still shows 12".

So here is the question is the MP gauge a required item on an aircraft with a constant speed prop? I asked around the airfeild and opions differed. So what do you all think?

Maybe it was okay and some say I was a wus for returning when all other indiacators where normal, but for me it was the right decsion.
 
Okay porably a real stupid question here, I went out to practice for my CFI checkride the other day. Climbed in the FBO Arrow preflight, taxi and runup all okay.

Just after takeoff at about 400' I looked down MP shows 12" ! Okay oil presure okay, oil temp okay mmmmm I elected to do an immediate return, land, taxi off full power run up still shows 12".

So here is the question is the MP gauge a required item on an aircraft with a constant speed prop? I asked around the airfeild and opions differed. So what do you all think?

Maybe it was okay and some say I was a wus for returning when all other indiacators where normal, but for me it was the right decsion.

Since you're prepping for the CFI, consider:

  • What are the legal requirements for Day, VFR flight?
  • How is airworthiness defined?
(Hint -- there are at least 3 components to airworthiness)
 
Okay porably a real stupid question here, I went out to practice for my CFI checkride the other day. Climbed in the FBO Arrow preflight, taxi and runup all okay.

Just after takeoff at about 400' I looked down MP shows 12" ! Okay oil presure okay, oil temp okay mmmmm I elected to do an immediate return, land, taxi off full power run up still shows 12".

So here is the question is the MP gauge a required item on an aircraft with a constant speed prop? I asked around the airfeild and opions differed. So what do you all think?

Maybe it was okay and some say I was a wus for returning when all other indiacators where normal, but for me it was the right decsion.

In Canada the reg is found in CAR 605.14 and says this:

605.14 No person shall conduct a take-off in a power-driven aircraft for the purpose of day VFR flight unless it is equipped with
[bunch of other stuff snipped]
(i) a manifold pressure gauge for each
(i) reciprocating engine equipped with a variable-pitch propeller,
(ii) reciprocating engine used to power a helicopter,
(iii) supercharged engine, and
(iv) turbocharged engine;


The US requirement is in FAR 91.205, I think. It'll look the same. It's the same section that requires fuel gauges and airspeed indicators and altimeters and so forth. A functioning instrument is implicit, so we can't say "I have an MP gauge; it just doesn't work." A manifold pressure gauge isn't a manifold pressure gauge if it isn't gauging manifold pressure.

This should be standard PPL groundschool stuff. I run into so many who don't know the requirements and it must be that it isn't getting covered because it doesn't show up on exams or something. This is called teaching to a test standard rather than teaching to a proficiency standard, and it's poor value for money paid, IMHO.


Dan
 
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... I asked around the airfeild and opions differed. So what do you all think?...
What does 91.205 say?

What does the equipment list in your POH say?
-harry
 
Okay porably a real stupid question here, I went out to practice for my CFI checkride the other day. Climbed in the FBO Arrow preflight, taxi and runup all okay.

Just after takeoff at about 400' I looked down MP shows 12" ! Okay oil presure okay, oil temp okay mmmmm I elected to do an immediate return, land, taxi off full power run up still shows 12".

So here is the question is the MP gauge a required item on an aircraft with a constant speed prop? I asked around the airfeild and opions differed. So what do you all think?

Maybe it was okay and some say I was a wus for returning when all other indiacators where normal, but for me it was the right decsion.

More than likely the gauge stuck. You could have continued the flight without problems.

The decision to return is yours to make.
 
Not from a regulatory perspective, no.
-harry

Show me where in the regs that state that when the MP gauge fails in flight you must make an immediate landing at the first suitable airport, or that you cannot continue the flight to the point of intended landing.

91.213 Inoperative instruments and equipment


(a) Except as provided in paragraph (d) of this section, no person may take off an aircraft with inoperative instruments or equipment installed unless the following conditions are met:
 
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Show me where in the regs that state that when the MP gauge fails in flight you must make an immediate landing at the first suitable airport, or that you cannot continue the flight to the point of intended landing.
91.205...

...no person may operate a powered civil aircraft ... unless that aircraft contains the instruments and equipment specified in those paragraphs ... and those instruments and items of equipment are in operable condition.
...
(8) Manifold pressure gauge for each altitude engine.
So you're not allowed to operate an aircraft with a failed manifold pressure gauge. Of course, once you've already taken flight, "not operating" isn't really an option any more. So what happens now? Well, I'm pretty confident the FAA would approve of me landing, as opposed to attempting to cease my operation while still in mid-air. I'm less confident that the FAA would approve of me continuing to operate that plane to the pancake fly-in 3 airports over, and then back.

Note that 91.213 doesn't even apply in this case, as it is only applicable to instruments not required under, for instance, 91.205.
-harry
 
A non-turbo Piper Arrow doesn't have an "altitude engine," so the 91.205(b)(8) requirement doesn't apply. However, a CFI applicant should know where to look in the AFM of that Piper to find out what's required for flight, including whether the MP gauge is required or not.

In any event, the decision to abort the flight after the gauge failed was prudent, and Chuck should tell anyone who says otherwise to bugger off because it's better to be down here wishing you were up there than to be up there wishing you were down here. Also, from a regulatory perspective, unless Chuck was sure the airplane was still airworthy with that failed gauge, 91.7(b) requires that he terminate the flight.
 
A non-turbo Piper Arrow doesn't have an "altitude engine," so the 91.205(b)(8) requirement doesn't apply. However, a CFI applicant should know where to look in the AFM of that Piper to find out what's required for flight, including whether the MP gauge is required or not.

In any event, the decision to abort the flight after the gauge failed was prudent, and Chuck should tell anyone who says otherwise to bugger off because it's better to be down here wishing you were up there than to be up there wishing you were down here. Also, from a regulatory perspective, unless Chuck was sure the airplane was still airworthy with that failed gauge, 91.7(b) requires that he terminate the flight.

The question here is where you terminate the flight. Once again, the regulations do not require an immediate termination of the flight once an instrument has failed in flight. The pilot can continue to the point of intended landing but once lands the item must be repaired before continuation of the next flight or return to the airport of departure, his choice. We can argue all day long at what point you "terminate" the flight.


If you would have bothered to read my original response you would have noted I said "The decision to return is yours to make." So perhaps you should be the one to "bugger off".

91.7 Civil aircraft airworthiness.

(a) No person may operate a civil aircraft unless it is in an airworthy condition.
(b) The pilot in command of a civil aircraft is responsible for determining whether that aircraft is in condition for safe flight. The pilot in command shall discontinue the flight when unairworthy mechanical, electrical, or structural conditions occur.


"Discontinue the flight" means at the next point of intended landing unless it's an emergency situation. I have actually had this discussion with the FAA in both Part 135 and 121 operations concerning in flight failures and this regulation and how it applies since this is always a topic under maintenance issues and application of the MEL's.



Losing a MP gauge on a normally aspirated piston engine is hardly an emergency, but then again it's up to the PIC to make the determination if he wants to continue or return.


 
I'm less confident that the FAA would approve of me continuing to operate that plane to the pancake fly-in 3 airports over, and then back.

You're correct in the assumption of continuing the flight back once you've landed. Once landed at your intended destination the instrument must be repaired and returned to service before further flight.
 
You're correct in the assumption of continuing the flight back once you've landed. Once landed at your intended destination the instrument must be repaired and returned to service before further flight.

A couple of months ago I lost a tach 5 minutes after takeoff. My choices were:
1) Continue to destination
2) Return to departure airport
3) Land at some airport along the way

I know the airplane -- every indication was the engine was performing normally. My clue that it was the tach and not the engine was the tach needle laying at the base of the glass.

I was closer to KLBE than KFWQ (by about 2 miles), but it made no sense to fly to LBE and then be stuck without a mechanic and without a ride.

So I cancelled IFR (was VMC), did a 170, and reurned to home base, where the local IA/A&P swapped in a new tach 3 days later.

I post this action here as my actions were in complete conformance with both the letter and spirit of the law.

There is no requirement that you dive bomb the nearest R or P field the moment you lose an instrument.
 
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Sorry you're wrong on this one.
Well, I got the definition of "altitude engine" wrong, so anything's possible, but let's look at the text of the FAR:
91.213 ... no person may take off an aircraft with inoperative instruments or equipment installed unless the following conditions are met:
(a) ...(1) An approved Minimum Equipment List exists for that aircraft.
...
(c) A person authorized to use an approved Minimum Equipment List
...must use that Minimum Equipment List to comply ...
...
(d) Except for operations conducted in accordance with paragraph (a) or (c) of this section, a person may takeoff an aircraft in operations conducted under this part with inoperative instruments and equipment without an approved Minimum Equipment List provided-
...
(2) The inoperative instruments and equipment are not-
...
(ii) Indicated as required on the aircraft's equipment list, or on the Kinds of Operations Equipment List for the kind of flight operation being conducted;
...
(iii) Required by 91.205 or any other rule of this part for the specific kind of flight operation being conducted...
I'm going to assume that an Arrow used for CFI training does not have a MEL, and so we can ignore (a) and (c) and focus on (d), which says that we can takeoff with an inoperative instrument as long as that instrument isn't "required" on the plane's equipment list, and isn't required by 91.205.

In this case, if the Arrow is a Turbo Arrow, then the MP gauge is required by 91.205, and thus 91.213 does not apply. Even if it's normally-aspirated, since the MP gauge appears as 'required' in the equipment list (per my Arrow manual), 91.213 doesn't apply.

In other words, 91.205 says: "you can't operate without this stuff", while 91.213 says "for everything else, you can takeoff with it broken, as long as you inactivate and placard it, etc".
-harry
 
Well, I got the definition of "altitude engine" wrong, so anything's possible, but let's look at the text of the FAR:
91.213 ... no person may take off an aircraft with inoperative instruments or equipment installed unless the following conditions are met:
(a) ...(1) An approved Minimum Equipment List exists for that aircraft.
...
(c) A person authorized to use an approved Minimum Equipment List
...must use that Minimum Equipment List to comply ...
...
(d) Except for operations conducted in accordance with paragraph (a) or (c) of this section, a person may takeoff an aircraft in operations conducted under this part with inoperative instruments and equipment without an approved Minimum Equipment List provided-
...
(2) The inoperative instruments and equipment are not-
...
(ii) Indicated as required on the aircraft's equipment list, or on the Kinds of Operations Equipment List for the kind of flight operation being conducted;
...
(iii) Required by 91.205 or any other rule of this part for the specific kind of flight operation being conducted...
I'm going to assume that an Arrow used for CFI training does not have a MEL, and so we can ignore (a) and (c) and focus on (d), which says that we can takeoff with an inoperative instrument as long as that instrument isn't "required" on the plane's equipment list, and isn't required by 91.205.

In this case, if the Arrow is a Turbo Arrow, then the MP gauge is required by 91.205, and thus 91.213 does not apply. Even if it's normally-aspirated, since the MP gauge appears as 'required' in the equipment list (per my Arrow manual), 91.213 doesn't apply.

In other words, 91.205 says: "you can't operate without this stuff", while 91.213 says "for everything else, you can takeoff with it broken, as long as you inactivate and placard it, etc".
-harry

For clarity it's about what to do when an instrument fails after take off. In the instance of the MP gauge you can simply go back or continue to your point of landing.

Like stated earlier, let's say you realize that where you're going has no maintenance so that after you land you're basically stuck until someone can go fix it, so in that instance it's wise to turn back. Or in the instance of the pilot training to be a CFI he didn't feel comfortable so he returned, once again no problem. Or in the other instance you decide to continue your trip and have it fixed after landing, again no problem.

Common sense has to prevail here. The FAA has always defined this as continuing to the point of landing. Also the last time I checked, the FAA doesn't ride along on every flight to insure everything is working nor have they implanted boxes on aircraft to alert them of when something fails. If you land at an airport and just so happens to be an FAA Inspector standing there and he sees the MP gauge indicating 12" while the engine is off at what point does the Inspector knows it failed? Did it happen right after takeoff or while you were on the downwind leg? All the Inspector will care about is that you have it properly repaired and legally returned to service before the next flight.
 
Common sense has to prevail here. The FAA has always defined this as continuing to the point of landing. Also the last time I checked, the FAA doesn't ride along on every flight to insure everything is working nor have they implanted boxes on aircraft to alert them of when something fails. If you land at an airport and just so happens to be an FAA Inspector standing there and he sees the MP gauge indicating 12" while the engine is off at what point does the Inspector knows it failed? Did it happen right after takeoff or while you were on the downwind leg? All the Inspector will care about is that you have it properly repaired and legally returned to service before the next flight.

Common sense may be trumped by considerations of the inevitable lawsuit after the crash.

"Ladies and gentlemen of the jury, the pilot continued the flight with a malfunctioning instrument -- as you've heard from expert testimony, a critical instrument. In fact, the FAA requires that instrument for flight in the very conditions of this crash. Therefore this pilot was clearly reckless, and did not consider the safety of his passengers -- now deceased -- or the innocent people on the ground...."
 
Common sense may be trumped by considerations of the inevitable lawsuit after the crash.

"Ladies and gentlemen of the jury, the pilot continued the flight with a malfunctioning instrument -- as you've heard from expert testimony, a critical instrument. In fact, the FAA requires that instrument for flight in the very conditions of this crash. Therefore this pilot was clearly reckless, and did not consider the safety of his passengers -- now deceased -- or the innocent people on the ground...."

Unbelievable, simply unbelievable.:nonod:
 
so what is the definition of an 'altitude engine' ?
 
ah interesting. I always just assumed that it was an engine that had a seperate throttle and prop control.
 
Googling around, the definition that seems to crop up is: "... a reciprocating aircraft engine having a rated takeoff power that is producible from sea level to an established higher altitude..."

If this comes from some authoritative source, I don't know what it is.

But assuming this definition, a normally aspirated piston engine can only produce its rated takeoff power at sea level, that power diminishes with increasing density altitude. But add a turbo...
-harry
 
The question here is where you terminate the flight. ... "Discontinue the flight" means at the next point of intended landing unless it's an emergency situation.
I can't speak to what some individual inspector told you, but the FAA Chief Counsel and the NTSB feel differently. See Administrator v. Gordon:
...we have interpreted section 91.7(b) as requiring -- upon the occurrence of an unairworthy condition -- a landing "at the first available point consistent with the safe operation of that aircraft." Administrator v. Genereaux, 4 NTSB 1245, 1247 (1984), (quoting the law judge's initial decision); Administrator v. Halbert, NTSB Order No. EA-3628 at 5 (1992).
But even if your interpretation was correct, I would still tell anyone who called Chuck a "wus" for turning back to bugger off. Safety is never enhanced by insulting someone who makes a cautious, even overly cautious, in-flight decision.
 
But even if your interpretation was correct, I would still tell anyone who called Chuck a "wus" for turning back to bugger off. Safety is never enhanced by insulting someone who makes a cautious, even overly cautious, in-flight decision.

Ron, if you are inferring I made such a remark, please reread my post, again.

"More than likely the gauge stuck. You could have continued the flight without problems.

The decision to return is yours to make. "

No where in this thread have I seen the assertion you are making that someone called this fellow a name for what he did.

Thousands of commercial flights happen each day and POI's at all the air carriers use the method I described. It's even been a discussion during type rides on the oral, so I guess the FAA is wrong on this too.

Common sense is once again being tossed out the window.

Later. :rolleyes:
 
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I can't speak to what some individual inspector told you, but the FAA Chief Counsel and the NTSB feel differently. See Administrator v. Gordon:

Ron, this case involves a guy landing gear up in a Navajo, then proceeding to fly to another destination with a badly damaged aircraft.

ABSOLUTELY has nothing to do with this thread and the routine failure of an instrument. Big difference between damaged propellers and an inop MP gauge.

This is a rather lame attempt for you to justify your argument.
 
mmmmmm I am going to go humbly back to my little corner and keep quiet, I am amazed that one question created such a ruckus.

Just for my own defense, in reading all avaliable books that I have to include the FAR's I had concluded that a MP gauage was required to operate an aircraft with a constant speed prop. This question rasied alot of heated conversation as well with other CFI's that I had talked to. Hence why I posed the question here.

chuck
 
mmmmmm I am going to go humbly back to my little corner and keep quiet, I am amazed that one question created such a ruckus.

Just for my own defense, in reading all avaliable books that I have to include the FAR's I had concluded that a MP gauage was required to operate an aircraft with a constant speed prop. This question rasied alot of heated conversation as well with other CFI's that I had talked to. Hence why I posed the question here.

chuck

Chuck, you are correct it is required for a plane with a constant speed prop. And your actions you took are appropriate. I was just trying to point out that it's not out of the question to have continued the flight.

I appreciated your question.
 
Ron, if you are inferring I made such a remark, please reread my post, again.
No, I am not, and was not. It appears you missed this part of Chuck's original post:
Maybe it was okay and some say I was a wus for returning when all other indiacators where normal, but for me it was the right decsion.
My comment that he should tell those who said he was a "wus" to "bugger off" was entirely directed to those who told him he was a "wus," not you. And I still feel that way -- people who call others offensive names for making a conservative inflight decision hurt, not help, aviation safety, and deserve to be told to "bugger off."
 
Ron, this case involves a guy landing gear up in a Navajo...
That interpretation of the reg, as meaning that an unairworthy aircraft is required to be landed "... at the first available point consistent with the safe operation of that aircraft..." is independent of the specifics of "how" unairworthy it is. They didn't say, "well, a really, really unairworthy aircraft must be landed asap, but otherwise, don't worry about it", they provided an interpretation of the reg that applies generally.

Here's another one:
http://www.ntsb.gov/alj/O_n_O/docs/AVIATION/3628.PDF
...It is agreed that from the moment respondent observed the oil pressure gauge fluctuation, the aircraft was not airworthy. Respondent decided not to land at Laramie Airport, Laramie, Wyoming, although it was close by when he shut down the engine, choosing instead to proceed to his original destination, Stapleton Airport...
...The standard to be followed when an aircraft becomes unairworthy in flight, however, is to land at the first location "`consistent with the safe operation of that aircraft.'" ... "The criteria is not that he discontinue the flight at the best point available consistent with the safe operation of the aircraft."...
-harry
 
Ron, this case involves a guy landing gear up in a Navajo, then proceeding to fly to another destination with a badly damaged aircraft.

ABSOLUTELY has nothing to do with this thread and the routine failure of an instrument. Big difference between damaged propellers and an inop MP gauge.

This is a rather lame attempt for you to justify your argument.
It's what the NTSB and FAA said, and I don't see anything in that case or the ones which set the precedent which says anything but "unairworthy." If the MP gauge is listed as required in the AFM, the airplane isn't airworthy without it, and if it fails in flight, the only legal precedents I can find say that legally you are bound to land at the first suitable airport. Of course, the odds of the FAA finding out that you pressed on with a bad MP gauge are about zip, but if the question is what does the law say, the answer is as I said.

I realize that Part 121/135 operators with ops specs and approved MEL's may have other options based on those FAA-approved documents, but the Part 91 flyers who make up the vast majority of the readers of this site (like Chuck) don't have MEL's or ops specs, and are bound by the rules stated. Deviate from them at your own risk; there is no reason to expect an argument that "it was only a minor item" to be availing if push comes to legal shove.
 
It's what the NTSB and FAA said, and I don't see anything in that case or the ones which set the precedent which says anything but "unairworthy." If the MP gauge is listed as required in the AFM, the airplane isn't airworthy without it, and if it fails in flight, the only legal precedents I can find say that legally you are bound to land at the first suitable airport. Of course, the odds of the FAA finding out that you pressed on with a bad MP gauge are about zip, but if the question is what does the law say, the answer is as I said.

I realize that Part 121/135 operators with ops specs and approved MEL's may have other options based on those FAA-approved documents, but the Part 91 flyers who make up the vast majority of the readers of this site (like Chuck) don't have MEL's or ops specs, and are bound by the rules stated. Deviate from them at your own risk; there is no reason to expect an argument that "it was only a minor item" to be availing if push comes to legal shove.

You're not an attorney. I emailed this over to a very good friend of mine who is a real attorney and I've maintained his plane for him for years.

His response:

"This wouldn't pass the "laugh test" (the judge laughs so hard he falls off the bench!) if this guy tried to use this as case law in your situation in regards to application of the FAR's you cited in the situation of someone having an instrument failure after takeoff. He clearly does not understand the issue at hand nor the applicability of case law."

That's all I got to say on that.

Good day. :D
 
That interpretation of the reg, as meaning that an unairworthy aircraft is required to be landed "... at the first available point consistent with the safe operation of that aircraft..." is independent of the specifics of "how" unairworthy it is. They didn't say, "well, a really, really unairworthy aircraft must be landed asap, but otherwise, don't worry about it", they provided an interpretation of the reg that applies generally.

Here's another one:
http://www.ntsb.gov/alj/O_n_O/docs/AVIATION/3628.PDF
...It is agreed that from the moment respondent observed the oil pressure gauge fluctuation, the aircraft was not airworthy. Respondent decided not to land at Laramie Airport, Laramie, Wyoming, although it was close by when he shut down the engine, choosing instead to proceed to his original destination, Stapleton Airport...
...The standard to be followed when an aircraft becomes unairworthy in flight, however, is to land at the first location "`consistent with the safe operation of that aircraft.'" ... "The criteria is not that he discontinue the flight at the best point available consistent with the safe operation of the aircraft."...
-harry

This was over shutting down an engine in flight, in a twin turbo prop then continuing on to the destination. The engine was shut down due to fluctuating oil pressure (btw, I'm typed in a SA227 so I understand). When I flew SA227's an engine shutdown inflight required an immediate landing whether it was shut down as a precaution or from failure.

Your argument still doesn't hold water and can only be summarized as comparing apples to bulldozers.
 
Is that a Part 23 certification requirement? It's certainly not a 91.205 rule.

It's in 23.1305

"(5) A manifold pressure indicator for each altitude engine and for each engine with a controllable propeller." (em. added).


Trapper John
 
I realize that Part 121/135 operators with ops specs and approved MEL's may have other options based on those FAA-approved documents, but the Part 91 flyers who make up the vast majority of the readers of this site (like Chuck) don't have MEL's or ops specs, and are bound by the rules stated.

Yes, commercial operators as well as private operators use MEL/CDL list. But what happens when you have an inflight failure of an item not covered under the MEL/CDL? Then you resort to FAR Part 91.

If you are inflight and an item fails you get out the MEL to see if it's defer able. If it's not (and many items aren't) then you check to see if any limitations are advised. If not, then you proceed to your destination and write the item up and the plane cannot leave until it's cleared. Very simple and straight forward.

Many years ago I was flying a Cessna 404 from Hattiesburg, MS to Little Rock Arkansas on a freight run. Right after takeoff the left engine tach generator failed leaving my left tach inop. We had no MEL for this item, I simply synced the left engine to the right and continued to LIT, landed and wrote up the item which was fixed by the morning departure. I evaluated my situation, it was a clear VFR night and no other issues so I continued.

The reason I cite the situation above this goes on daily in all operations. Pilots do not terminate the flight immediately for an instrument failure. If they did you would see multitudes of airplanes making diversions everyday. And the FAA backs it up.
 
It's in 23.1305

"(5) A manifold pressure indicator for each altitude engine and for each engine with a controllable propeller." (em. added).


Trapper John

FAR 23 doesn't directly control what's required for airworthy flight, just what's needed for certification. If there's a related FAR that says to put something in the limitations section of the POH requiring the gauge then this would have an actual effect on us pilots.

For a counter example I think (too lazy to read) that fuel gauges are required by part 23 but airplanes can be legally flown in some cases when one or more gauge is inop.
 
This was over shutting down an engine in flight...
There's nothing in the interpretation that suggests it's specific to any given level of "seriousness" of instrument failure, though you keep acting as if it's just a judgment call.

Your claim is that "discontinue the flight" means "point of intended landing, unless it's an emergency". Both of the cases mentioned so far have given a very clear interpretation of "discontinue the flight", and they both agree it means "land at the first safe airport".

So far, you've presented nothing to support your cause, except a misinterpretation of 91.213, "I had a discussion with the FAA", and "I have a friend who's a lawyer".

That's fine, but I wouldn't bank on that interpretation in my own flying, nor would I recommend it to others. We have examples where judges decided we must land at the first safe airport, I have seen nothing so far that supports your more generous interpretation.

You seem to be interpreting a reg that requires us to "discontinue" as saying that we can "continue".
-harry
 
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