182 crashed into trees at Porepunkah
The only time a NVFR flight would be operating lower than 3000ft AMSL or 1000ft AGL would be in accordance with subregulation 91.277(3) of CASR - taking off or landing or within the NVFR circling area of an aerodrome (within 3NM)
We operated from our own lit airstrip carrying out VMC, NVMC, IMC flights, the strip was effectively at sea level and our operations were over water, LSALT was 1,900, dictated by an ABC radio transmitter on a hill, rarely did we get as high as 3,000AMSL, that's nose bleed territory for a helo pilot.
Our VMC limit over water in our operating area was clear of cloud, 350', 3k vis, didn't specify day or night 
The people answering the questions may be confident as to the validity of their conclusions and the relevance and accuracy of the facts they assert
CASA's 'Regulatory Guidance Delivery' folk omitted what I consider to be fundamentally important, intersecting definitions
Hmmm, my guess is CASA's 'Regulatory Guidance Delivery' folk will argue that the 'flight visibility' criterion - how far you can see forward from the cockpit - is different from the requirement to operate in sight of the ground or water (whenever at or below ....).
Hmmm, my guess is CASA's 'Regulatory Guidance Delivery' folk will argue that the 'flight visibility' criterion - how far you can see forward from the cockpit - is different from the requirement to operate in sight of the ground or water (whenever at or below ....).
Example: 'visibility' in the definition above - "the ability.. to see and identify prominent unlighted objects by day and prominent lighted objects by night".
You only have to "see and identify" "prominent lighted objects" by night - not unlighted ones, not the ground, not the hills, or the moon or the clouds... prominent lighted objects. If there are no lighted objects (especially prominent ones), then, by that definition, you don't have to see them. See??
Hmmmm, if you go to Table 2.07 in MOS Part 91, the 'flight visibility' column (4) is separate from the 'operational requirements' column (6). So if we take my favourite item for present purposes - Item 4 - the 'flight visibility' column says "5 000 m" and the 'operational requirements' column says "Aircraft must be operated in sight of ground or water".
Given the definition of "flight visibility", the "5 000 m" seems to me to mean that the atmospheric conditions in flight (note: "flight" is also defined) must be such that when you look forward from the cockpit you are able to see and identify all "prominent unlit objects by day" and all "prominent lighted objects by night" that are 5,000 metres or closer to you in that direction. If there happen to be no such objects 5,000 metres or closer to you in the forward direction from the cockpit, it does not matter that you cannot see and identify objects that do not exist. But the atmospheric conditions must be such that you could if they did.
I do not think it follows that the separate operational requirement can be interpreted as meaning that the aircraft must be operated in sight of ground or water, unless the ground or water cannot be seen from the cockpit. As I've said before, that would render the operational requirement meaningless.
What we don't know is the level of detail that must be discernible. I don't think it goes as far as "every tree, chicken coop, horse and cow".
And I reiterate, all of this is why the old and not so bold 'weekend warrior' NVFRers I know only do it on moonlit nights.
Given the definition of "flight visibility", the "5 000 m" seems to me to mean that the atmospheric conditions in flight (note: "flight" is also defined) must be such that when you look forward from the cockpit you are able to see and identify all "prominent unlit objects by day" and all "prominent lighted objects by night" that are 5,000 metres or closer to you in that direction. If there happen to be no such objects 5,000 metres or closer to you in the forward direction from the cockpit, it does not matter that you cannot see and identify objects that do not exist. But the atmospheric conditions must be such that you could if they did.
I do not think it follows that the separate operational requirement can be interpreted as meaning that the aircraft must be operated in sight of ground or water, unless the ground or water cannot be seen from the cockpit. As I've said before, that would render the operational requirement meaningless.
What we don't know is the level of detail that must be discernible. I don't think it goes as far as "every tree, chicken coop, horse and cow".
And I reiterate, all of this is why the old and not so bold 'weekend warrior' NVFRers I know only do it on moonlit nights.
The note in the Exposure Draft of Part 91 (MOS for 91.1035 Aircraft Performance) is also relevant: “It is the intention that CAOs 20.7.4. …. will be subject of a project to review them and provide guidance material in the form of an AC in the future. Much of the content of the CAOs contain either certification standards or outdated information. CASA expects pilots to operate in accordance with the aircraft flight manual (AFM). All performance information in the AFM is produced and complies with the aeroplane certification standards.”
Now we have Part 91 and that promised AC 91-02 which is very sensible - it recognises different, older certification standards including those types for which there is no performance information. "The different certification standards specify what information must be provided in the AFM/pilot operating handbook (POH).... some aircraft are not required to have performance data and, where there may be some information, it may not always be relevant to the actual operation being performed." Of course "Regulation 91.095 requires the pilot to operate in accordance with the 'aircraft flight manual instructions'." The Limitations section of the AFM is illuminating.
Not sure about rubbish, but a while back an NTSB report into a PA-31 crash highlighted a major factor being that the aircraft was operating outside the performance data envelope. It was back from the 80s or 90s, so haven't got the time to dredge it up. The NTSB seemed to be saying that the performance chart limits were also the environmental limits for operation and the aircraft should not have been there. Goes back to the rule you can interpolate between lines, but not extrapolate beyond them. I think Piper covers up to ISA +20 and stops there, which means around 35C at SL is the max temp for operation. While they are now based in Florida, the original plant and testing was in Pennsylvania, where ISA +20 is not common, so fits.
PS the short of it was that the commuter Navajo could not maintain altitude while well within the loading envelope and crashed en-route on a very hot day in the mid-west. Pretty sure litigation was being aimed at Piper who may have made a statement that the charts are the limits and operating outside of the charted lines was not endorsed by the manufacturer.
I mean you could say it's not a hard limitation as such, but similar to oil grade in your engine. Run the wrong SAE grade of oil intentionally the engine will damage and fail, you could be held responsible for what is damaged. If you are running 10W-30 oil its max recommended ambient is 30-35c, is it safe to operate above that, probably for short duration. If it's 10W-40 it gets up to 40C but not recommended above that. Avgrades W080/W100 are basically similar to SAE-10W-30 with W100 maxing out at 30C recommended.
PS the short of it was that the commuter Navajo could not maintain altitude while well within the loading envelope and crashed en-route on a very hot day in the mid-west. Pretty sure litigation was being aimed at Piper who may have made a statement that the charts are the limits and operating outside of the charted lines was not endorsed by the manufacturer.
I mean you could say it's not a hard limitation as such, but similar to oil grade in your engine. Run the wrong SAE grade of oil intentionally the engine will damage and fail, you could be held responsible for what is damaged. If you are running 10W-30 oil its max recommended ambient is 30-35c, is it safe to operate above that, probably for short duration. If it's 10W-40 it gets up to 40C but not recommended above that. Avgrades W080/W100 are basically similar to SAE-10W-30 with W100 maxing out at 30C recommended.
Last edited by 43Inches; 24th Jan 2023 at 23:14.
Consider an example of an LSA where the POH only has take-off and landing data for ISA SL, nil wind and a sealed runway. Just one number for take-off and another for landing. AC 91-02 provides guidance on how to extrapolate that data, conservatively, to get performance data at a higher elevation on a hot day etc. Performance tables for my airplane go to 6,000 ft pressure altitude and 40°C. The latter is not a limitation per the manual and AC 91-02 provides guidance on using density altitude to get performance at higher ambient temperatures - that is not extrapolating, is it, because I am still working within the range of density altitudes derived from the data.
Moderator
Putting to one side whether there be a legal constraint or not with the performance section data - as opposed to specific limitations in the limitations section, one of the problems faced by the pilot is "how do I go about extrapolating in an appropriate manner " ? That is to say, here I am, ready to go, and the temperature (or whatever parameter) is a bit outside the POH chart/tabulated data - should I, or shouldn't I go ?
While all the charts are based on the same sort of underlying equations, with variations and tweaks to suit, the typical pilot has no reasonable means of making a technically defensible assessment of what the story might be with a bit of extrapolation. No matter what anyone suggests, one of the principal concerns is being able to defend one's actions and decisions in court, after the event, should it all turn to custard on the day.
The old DCA P-charts (Bob Tait was responsible for chart format "titles" morphing to "Cessna", "Piper", and "linear" charts - those being the first examples of the particular styles which he had seen) had the advantage that DCA published internal tech memos which prescribed how they went about producing the charts back in the days of the old Civil Mk. 1 and 2 AFMs. Most of us who worked in this area have copies of those documents and used them back in the old days. With the report equations, one just ran the expansions and finished wherever one chose. Had one gone a bit further, the approved chart would have reflected that wider range in variable quantities. The base data position usually would be from quite simple flight test work or, in one case I recall, where DCA rejected the OEM's charts, we agreed on an OEM specific chart point which they would accept and then proceeded to use that for the expansion. Interestingly, when I ran that particular exercise, the values I obtained compared to the OEM figures showed some measurable variation. John F had a very good nose for smelling out suss data.
Chaps such as djpil, aeromariner (still drops in, but hasn't posted for quite some time), and others, have the memos and are more than competent to run such extrapolations in a manner which provides for a defensible position in court - but how should the typical pilot without our engineering backgrounds cope ? About the only way is to run with the rules of thumb corrections which have been published by some of the NAAs.
I can't see any major problem with minor expansions in the field with one caveat - there may be specific characteristics of the aircraft which give rise to discontinuities which are, effectively, hidden from the user. However, he who extrapolates should have a sound and sensible story for the subsequent talk fest.
While all the charts are based on the same sort of underlying equations, with variations and tweaks to suit, the typical pilot has no reasonable means of making a technically defensible assessment of what the story might be with a bit of extrapolation. No matter what anyone suggests, one of the principal concerns is being able to defend one's actions and decisions in court, after the event, should it all turn to custard on the day.
The old DCA P-charts (Bob Tait was responsible for chart format "titles" morphing to "Cessna", "Piper", and "linear" charts - those being the first examples of the particular styles which he had seen) had the advantage that DCA published internal tech memos which prescribed how they went about producing the charts back in the days of the old Civil Mk. 1 and 2 AFMs. Most of us who worked in this area have copies of those documents and used them back in the old days. With the report equations, one just ran the expansions and finished wherever one chose. Had one gone a bit further, the approved chart would have reflected that wider range in variable quantities. The base data position usually would be from quite simple flight test work or, in one case I recall, where DCA rejected the OEM's charts, we agreed on an OEM specific chart point which they would accept and then proceeded to use that for the expansion. Interestingly, when I ran that particular exercise, the values I obtained compared to the OEM figures showed some measurable variation. John F had a very good nose for smelling out suss data.
Chaps such as djpil, aeromariner (still drops in, but hasn't posted for quite some time), and others, have the memos and are more than competent to run such extrapolations in a manner which provides for a defensible position in court - but how should the typical pilot without our engineering backgrounds cope ? About the only way is to run with the rules of thumb corrections which have been published by some of the NAAs.
I can't see any major problem with minor expansions in the field with one caveat - there may be specific characteristics of the aircraft which give rise to discontinuities which are, effectively, hidden from the user. However, he who extrapolates should have a sound and sensible story for the subsequent talk fest.
John, just had a thumb through of the performance section of a C207 manual and I don't see anything that constitutes a temperature limitation. The only charts that come close is the take off, landing and rate of climb which are only tabulated to 40°C against pressure altitude, but all of those can be addressed by means of calculating the density altitude, maybe I'm missing something, I'd assume all our lighty manuals would be similar. Some aircraft do have temperature limitations listed in the limitations section, my workaday FAR 29 type was -34°C to ISA plus 37°C not to exceed 49°C.
Moderator
In usual parlance, the limitations section is hard, other sections not quite so.
For instance, it is quite routine for airlines to seek an NTO (no technical objection) from the OEM for airline initiated variations to OEM published protocols. However, one would need to have one's ducks in a row to provide for a defence in court where one operates other than in accordance with the black and white of the AFM.
As, I think, we all appreciate, on occasion it is a matter that the end parameter was either a convenient termination chosen by the OEM or, for example in the case of cross wind testing, the best that they could find during the program.
For instance, it is quite routine for airlines to seek an NTO (no technical objection) from the OEM for airline initiated variations to OEM published protocols. However, one would need to have one's ducks in a row to provide for a defence in court where one operates other than in accordance with the black and white of the AFM.
As, I think, we all appreciate, on occasion it is a matter that the end parameter was either a convenient termination chosen by the OEM or, for example in the case of cross wind testing, the best that they could find during the program.
And this is the crux of aviation law, very rarely will you be prosecuted for these breaches without something going wrong first. If you were to load up a Navajo and take off at 40C lose and engine and injure several people you will then be under the microscope, as the injured will want a ruling of who's responsible under law. Piper is going to claim you were outside the operating envelope for the aircraft, as there were no charts to prove you could climb. The engine manufacturer will come up with several reasons why its not their fault it failed. The engineers know how to produce paperwork that it was all fine until you flew it. Leaving the the dunce in the left seat who thought they knew how to extrapolate and knowingly flew beyond the lines. Good luck convincing the lawyers that you were not negligent and owe millions to the passengers.
Of course if the manual says what to do and how to extrapolate safely, fill ya boots the manufacturer has given permission to do so. But without express permission from the manufacturer and details how to you are probably on the wrong side of the grey border.
And using density charts to extrapolate in extreme heat is troublesome, as engine, wing, oil and fuel systems all deteriorate performance with non linear drop off, in fact it could be quite sharp performance loss at high temperatures as nothing on the aircraft may be designed for it.
PS; food for thought, a Ships Captain was charged today over choosing to sail in poor weather across Bass Strait. It led to the deaths of a number of cattle on board the ship. Fined $15,000. Shows that aviation is not the only area where you can get caught by the courts for pushing bad weather. Where does it specify when a sailing must be abandoned due to weather with cattle on board, well that just comes down to the Captain. If they die or are injured it was too rough regardless...
Of course if the manual says what to do and how to extrapolate safely, fill ya boots the manufacturer has given permission to do so. But without express permission from the manufacturer and details how to you are probably on the wrong side of the grey border.
And using density charts to extrapolate in extreme heat is troublesome, as engine, wing, oil and fuel systems all deteriorate performance with non linear drop off, in fact it could be quite sharp performance loss at high temperatures as nothing on the aircraft may be designed for it.
PS; food for thought, a Ships Captain was charged today over choosing to sail in poor weather across Bass Strait. It led to the deaths of a number of cattle on board the ship. Fined $15,000. Shows that aviation is not the only area where you can get caught by the courts for pushing bad weather. Where does it specify when a sailing must be abandoned due to weather with cattle on board, well that just comes down to the Captain. If they die or are injured it was too rough regardless...
Last edited by 43Inches; 25th Jan 2023 at 22:47.
I see that the newish Xtreme Decathlon comes with an AFM per a recent amendment to FAR 23. The required performance information goes up to 40°C per that version of FAR 23 plus the Limitations section states:
49°C !
1.12 Outside Air Temperature Limits
Adequate powerplant cooling has been demonstrated for outside air temperatures below
120°F.
Adequate powerplant cooling has been demonstrated for outside air temperatures below
120°F.
Thread Starter
Last time I checked, a Decathlon doesn't come with air-conditioning.. so stuff the plane - the other performance aspect to consider is whether or not the pilot can safely operate in those temperatures!!!
I'd be heading for the nearest (beer) fridge.
(In my early training shortly after first solo, I was so keen to get flying in Melbourne's changeable weather that I got one-eye focussed on doing circuits at YMMB one day without noticing the forecast 35°C temps. I completed one circuit and prompted landed and taxiied back to the flight school.)
I'd be heading for the nearest (beer) fridge.
(In my early training shortly after first solo, I was so keen to get flying in Melbourne's changeable weather that I got one-eye focussed on doing circuits at YMMB one day without noticing the forecast 35°C temps. I completed one circuit and prompted landed and taxiied back to the flight school.)
It still does not specify particularly that you can fly up to that temperature, just that the engine should perform without overheating. It also does not say you can not exceed 49C, just that the engine will not cool adequately. The other issue with that statement it does not quantify what atmospherics accompany that temperature, what if it was 49C at 10,000ft Elev, I doubt the engine would cool well then if it was still capable of high power.
If you were to load up a Navajo and take off at 40C lose and engine and injure several people you will then be under the microscope, as the injured will want a ruling of who's responsible under law. Piper is going to claim you were outside the operating envelope for the aircraft, as there were no charts to prove you could climb.
Earlier I mentioned an accident in the USA where a Navajo crashed following an engine failure when it was ISA+ 30 or so. The NTSB queried Piper about its charts and the statement from Piper was that the lines were considered the environmental envelope for their aircraft. Therefore the aircraft was considered outside of it's environmental conditions if operated beyond the lines on the chart which equates to ISA +20. What that means is no performance could be guaranteed by Piper beyond those lines and they can not be held responsible if the aircraft did not climb, maintain altitude etc.... It becomes the PICs sole responsibility if they chose to fly on such a day. And if you should have an accident the responsibility and liability would fall on the PIC alone, not the manufacturer.
That's completely at odds with what Cessna Wichita have to say, if the temperature is greater than depicted on the chart for the specific altitude you may calculate the density altitude then use the temperature and altitude which will give the same density altitude. The example I used when I communicated with them was for a C404 take off distance at sea level on a 50°C day which gives a DA of 4,200, but the chart only goes to 40°C. Going to 40°C and pressure altitude of 1,000 gives a DA of 4,238, they deemed that an acceptable technique. Aircraft and engine performance is all about density altitude.
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That's completely at odds with what Cessna Wichita have to say, if the temperature is greater than depicted on the chart for the specific altitude you may calculate the density altitude then use the temperature and altitude which will give the same density altitude. The example I used when I communicated with them was for a C404 take off distance at sea level on a 50°C day which gives a DA of 4,200, but the chart only goes to 40°C. Going to 40°C and pressure altitude of 1,000 gives a DA of 4,238, they deemed that an acceptable technique. Aircraft and engine performance is all about density altitude.
PS the other issue at play is at what temperature do you stop extrapolating, at some point the engine and accessories will not be able to cope with the heat and power will reduce significantly more than linear, parts will start to bend and bloat due to the heat, maybe even melt, fuel will form vapor locks and so on. We had one PA28 that was painted black and it it's wing oil canned above 30c due to expansion, was disconcerting for pilots when metallic noises came from the wing, good reason not to paint things black when it's hot. While Cessna and Piper don't give an environmental envelope it's pretty obvious that over ISA +20 all piston engines start to struggle. The opposite applies at low temperature below ISA -20 plastics and rubbers start to become rigid and not return to form or become brittle and tear and not flex, oils and lubricants become thick, that's before even considering ice on the airframe.
Chieftains and Navajo engines really don't like the high 30c and 40c, have to use cowl flaps to manage heat and that reduces performance significantly. If you then had a failure the engine is most likely going to overheat at MCP pretty quickly, leaving you with the choice of cook it or descend.
Last edited by 43Inches; 31st Jan 2023 at 21:03.