CASA opinion: Aircraft must be grounded in temps over 40 degrees
 

An interesting item in the latest Vic RAPAC minutes.

Someone - perhaps unwisely - asked CASA for clarification of operations above 40 degrees C, given that the performance information in many flight manuals only goes up to 40 degrees.

"if an aircraft's AFM caps performance data at 40C, can the aircraft still legally fly when the ambient is above 40C?"

CASA's response:
"If ambient conditions exceed ... the range for which performance data is provided, the aircraft must be grounded"

I'm not sure whether the person who wrote that has actually looked at the performance data provided in a typical flight manual. There are many conditions for which no performance data is provided, so a prohibition on operating in conditions without performance data is not exactly workable.

Looking at e.g. a C172 manual, there is no performance data for any of the following:

• Flaps 0 takeoff
• In fact, nothing for normal takeoffs and landings - all performance data is for short field techniques
• Any runway slope
• Wet grass etc.

Common sense seems to have left the building

https://www.casa.gov.au/files/vic170323pdf

My mate in central WA is going to be in strife, he regularly flies in temps closer to 50 deg!

Hmmm... is this 'advise' dated April 1st ?

As far as i'm aware, Ambient temp is where yer standing and is not in any met reports. So in the middle of sumer standing next to yer aircraft in the middle of a large expanse of hot bitumen it would likely go past 40º even when the met says 35º.





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Just like all the POH's that describe one thing on one page, yet turn the page and the engineering data clearly says the opposite. You can't do both, so which do you trust?

Critical thinking is required folks, something many at CASA are incapable of doing, and demonstrate it regularly.

Measured where by who?

Presumably where-ever you are supposed to get the temperature from for your performance calculations.

OAT gauge, ATIS, AWIS, forecast... possibly even declared density?

By the pilot wherever they can get a temperature reading that makes it legal to fly.....

Saab 340B engine start limit 47C so at Birdsville eg. a clever fast look at the temp got you going..

In one middle east country, I hear that the temp never goes above 50c as that is when the tarmac workers have to stop work!! Helps keep the aircraft flying as well......

At Weipa they once used sprinklers on the tarmac to prevent it from melting.

Essentially you can't operate any aircraft legally if the AFM doesn't have performance data to support the conditions.

I once worked for a company in PNG who owned two Bell 412s, the AFM only had P charts to support ops below about 8000 ft, which technically prevented us from using the machines at high altitudes. Only solution was to purchase high altitude P charts from Bell which come at a cost.

Similar situation with some GA fixed wing aircraft in PNG, however most operators never bothered getting amended P charts.

So at 39.99 degrees you are good to go, but not at 40.1? Makes sense really.

So in the example of a C172, is it illegal to use the AFM documented normal takeoff or landing procedures? There is no performance data for them.

What about wet grass? A runway with a slope?

Someone - perhaps unwisely - asked CASA for clarification...


AndrewR - and that's when the fight started!


(In my opinion, it is Very Unwise Indeed to ask for clarification....particularly from the Cherubs Against Sensible Aviation.)

Extract from the SR22 POH. I have added the bolding


and

So even though the performance data is only given for temperatures up to 40 degrees the POH wording makes it clear that operation at higher ambient temperatures is not prohibited.

Would one be able to contend that if there is no explicit temperature in the limitations section, that the "40 deg limit" obtained from the P charts might not actually be a limit?

I am sure that is what the manufacturer intended, however CASA has said

"If ambient conditions exceed ... the range for which performance data is provided, the aircraft must be grounded"

In the SR22 POH they don't provide takeoff distance data for less than 0 degrees C. Does CASA really mean that the aircraft can't fly in temperatures less than O degrees C?

Andrew, yes, but they are not always correct. I'm sure you've probably experienced it.

Are aircraft to be grounded when the crosswind is greater than the demonstrated maximum?

If a place is hotter than forecast when you arrive overhead, and outside the P chart temp, they say you cannot land. Must the PIC now declare an emergency? Or will we have to hold alternates for the temp being too hot? Nothing in the AIP about that under alternate requirements!

My guess is that CASA partly, at least, bases their opinion on CAO 20.7.4 which changes the scope of this discussion.
e.g. " An aeroplane must not take off at a weight in excess of the least of the weights determined in accordance with subparagraphs (a) to (d):
(a) a weight at which the take-off distance required under subsection 6 for the pressure height, temperature, runway slope (if in excess of 1%) and wind component along the runway, is equal to or less than the take-off distance available in the direction of take-off. Approved declared conditions may be used instead of actual pressure height and temperature ..." etc.
i.e. if the performance information stops at 40 deg C (per FAR 23) then how can the pilot show compliance with CASA performance requirements at higher temps .....

The CAO argument is interesting.
It says you cannot take off at a weight greater than that determined from the P charts. But what if you cannot determine a weight?

You might not be able to show compliance, but can CASA prove, based on the same (lack of) performance information that the plane wouldn't perform?

Is there a specific regulation that explicitly states that you cannot operate outside the P chart figures?

Im just being a little bit of an advocate for the devil; I'm not necessarily brave enough to take on the potential battle.

My other question is- why only now does CASA say that you cannot operate when the temp is outside the P chart temperature? They've been in existence for decades, and it's not a new idea.

Further to djpil's comments ... the important thing is can you argue your case satisfactorily if push comes to shove and you find yourself in court for whatever reason ?

So far as performance is concerned, provided there is not an OAT limitation in the limitations section of the POH, one can always get the charts redone to suit your operational needs.

Just an observation that perhaps CASA are drawing on this section of the FARSome aircraft have a piece such as this in the limitations sectionPiper and Cessna, and others, have adopted the standard + 30 approach, with charts only going to 40C.

Question is, are you breaching the law by operating in temperatures above the certification standard when there is no limitation in that part of the manual?

Of course if you do the result can be

https://www.youtube.com/watch?v=OVM3RRd1vf0

I remember in a previous life flying a King Air 90 into YWDH. Temp on the OAT gauge was ISA+ 42 so I told the pax we will sit in the shade and waited for the gauge to show ISA + 39. This was my decision based on the fact that IF something went wrong it would be MY fault for operating outside the certified envelope. Ultimately its a Command decision-but to operate outside the certified envelope is incredibly poor Airmanship unless under EMG/Mercy Flight conditions.

How would you determine the runway required for a normal takeoff (no flaps) in a C172 at sea level, 15 degrees C?

I'm no lawyer, but CASA's insistance on "strict liability" clauses in virtually every regulation they produce makes a pilot's position quite clear. If you have an accident, and a possible/probable cause of the accident was a breach of a "strict liability" regulation, then you are in serious trouble.

Now the minutes of a RAPAC meeting do not constitue a strict liability regulation.

But if you do ding one in operating outside of the available performance data, and CASA believe that that was a contributing factor (and I'm sure they will try hard to do so), then you may fall foul of one of their "strict liability" regulations unless you can prove some reasonable means of compliance (kind of making you guilty unless you can prove innocent, which goes against most modern legal justice systems).

But also, don't ask a question unless you already know and like the answer. What else did they expect CASA to say: eg "yeah, no worries, just take off anyway, just don't ding it in..." :)

I'm sure a Pprune bush lawyer will pick apart what I've put, but that's my basic interpretation.

More straightforward when we had the Australian specific DoT AFMs but they've been discarded and the requirements of CAO 20.7.4 re soft dry grass and runway slopes don't fit with an older typical FAR 23 AFM or POH and the weasel words in the CAO are not enough to hang your hat on.

Nil authority to continue to use those old P charts, if you do then you are personally responsible - I asked CASA to provide the test data and analysis for the 8KCAB Decathlon and got nowhere. I suspected that some bright person had provided an 8KCAB with 180 hp and C/S prop for the performance testing - where did that leave me with an 8KCAB fitted with the standard 150 hp and FP prop? The P chart is simply labelled 8KCAB. Manufacturers info? - that's another story.

Interesting question and a lot of focus on the POH...

I'm no stranger to GA in hot climates, but perhaps the question some should be asking is "how long can my human body perform in 40+ degree temperatures without a whiff of air conditioning in a c172". I've done some fairly stupid things when I've been hot and dehydrated, and when that door shuts and the sweat starts dripping, don't expect your mental capacity to be at an all time high.

I can remember years ago taxiing in a Chieftain at YBDV for final destination YBOU (with stops at Roseberth and Durrie Stations) with the OAT gauge reading 48C.

On arrival at YBOU the OAT read 51C.

Struth Johnno;(if you are reading this) How did we survive this????:eek::rolleyes:

I'm kinda glad that the AUSTER doesn't have an AFM or a POH.

Kaz

Your decades-long trail of dangerous operations have been noted, kaz. :}

I'm now wondering how the old Perf charts were created.
Looking at the Takeoff Performance chart for a PA28 I see that the OAT region goes from -40'C to +40'C, but I seriously doubt that the PA28 was actually tested at -40'C.

Performance is determined from the Pressure (Density) Altitude.
The problem is that DA is non-linearly dependent on OAT.
Back in the 60's it was easier to pre-calculate a nomograph for the 'expected' operating range and +40'C seems like a reasonable upper limit for the USA at that time.
Now if I can determine what the DA actually is (from an expanded pre-calculated DA v OAT chart, or from a formula), then I can apply that DA to the Perf chart and on that basis the 40'C 'limit' is no longer a limit.

Unfortunately we are talking about CASA and their ineffable bureaucratic wisdom, so common-sense is not allowed.

FAR 23 has rules about the limits for extrapolating test data to higher or lower temps and altitudes.

They (we at times) used to do a short series of takeoff and landing tests at a place like Bacchus Marsh and a fancy (for then) computer program would print those P charts.
Charts also for climb performance limits apply to some types - remember that little line on the C150 P charts derived from a goround with flap down.

Just can't wait until an FOI rocks up for some refresher training.

Had an experienced back in the 70s where an aircraft departed in high temps 40+ but with a 20Kt wind that allowed a shorter, but into wind, runway to be used.

The Alphabet Authority (cannot remember what they were called at that particular point of time) tried to ping the pilot for departing of the runway as it was too short based on the "P" charts that only presented calculations to a temp of 35c and a wind less that the actual wind.

But using the manufacturers charts the aircraft could depart. The Alphabet Authority pointed out that we had to use the "P" Charts. I informed the Alphabet Authority that their "P" charts did not reflect the conditions experienced in Australia and therefore we were being forced to use charts unfit for purpose.

I did not hear back from Alphabet Authority.

Lucky Kaz...all operating Auster stuff in the brain database. No book.

I have some Auster type AFMs.... J2, J5F etc. Not heavy duty tho.

8. Glider towing.
Fly as normal.

Simple and sound advice.

Of course. Same as if MTOW is 2800Kg. You are good to go at 2800kg but not at 2801kg.

Go in to a pub the night before your 18th birthday, fly a charter before your new licence is issued...

Blah blah blah. There is always a line somewhere.

Ask this CASA guru for WRITTEN confirmation of this OPINION.

Yes but it the ATSB who would determine that.

I'm now wondering how the old Perf charts were created.

Further to djpil's comments ..

In days of olde .. when we had local rules (ie pre-Yates Report changes), one could either do one's own thing (ie develop equations or use the standard FT equations) or use the DCA equations (presented in an in-house document to which Industry consultants had access). Needless to say, most folks used the DCA document as that avoided much discussion in the approval process.

The DCA document (I have a copy but can't recall the ID without digging in the archives for it ..) used some pretty simple equations but, in practice, they were of sufficient accuracy that the P-charts were a reasonably good mix of a little conservatism and accuracy.

Later on, the document was revised the better to take account of turboprop performance .. and that document was a different beast altogether .. so, we ended up using the old stuff for pistons and the new stuff for turboprops.

The equations allowed for the interpolation (and limited extrapolation) of whatever data set had been captured .. not too much in the way of extrapolation as that involved a leap of faith .. interpolation was much more defensible. So far as test programs were concerned, we normally tried to get low/high and hot/cold within the realms of reasonable possibility and take it from there. Obviously, the more test data, the more accurate the end charts could be. What variable range ended up in the charts depended a lot on what range of test data could be found. This is no different to the problems faced by Mr Boeing and others ..

At the high end of the spectrum, for data capture, one could do cinetheodolite performance takeoffs and landings which provided a movie tracking record of the aircraft (allowing corrections for camera unit mistracking) and azimuth/elevation data for the camera axes (paper trace .. great fun working with that stuff).

Accurate survey data was required for the runway and camera unit position to do the geometry sums.

From these records, one could spend copious numbers of (relatively) productive hours developing a very accurate time history of the takeoff/landing distance and air distance/height. This allowed speed and acceleration data to be determined to a very good accuracy if you had a need for that sort of stuff.

Unfortunately, back in the 60s/70s, this equipment was pretty high tech (and expensive) so only the military and the likes of GAF were able to use it. Djpil and I spent numerous hours in the Fishermens Bend sweatshop doing this stuff after Nomad flight trials. Also, I had fun doing similar stuff at ARDU for a while.

Once we get out into the GA world, though, no-one was likely to have this kit sitting around waiting for some trials so the local industry, with DCA, developed a much simpler exercise using a reasonable quality still camera to take a series of exposures to get the important sections of the takeoff and landing. Not quite as accurate as the CT .. but much quicker and more than fit for purpose.

Some folk, to save on dollars, did the exercise with constant (gross weight) speeds throughout (reduced the number of flight trials required) and that produced some strange results in the P-charts which were the occasional subject of bar room discussions. For example, one saw landing P-charts where the distance increased with reducing weight (due to float at the end of the landing flare)

On occasions, if the OEM data in the POH appeared defensible, one would negotiate with the DCA gurus of the day and, sometimes, take a few points from the OEM POH data and use those to develop the P-charts.

DCA had a nice little HP plotter gadget to run up the charts .. most of us out in the Industry did it by hand .. same result... the typical P-chart presentation was dreamed up by DCA (Ron S, perhaps ?) and was just one of a range of possible presentations. It has its good and bad points, like any presentation. I did my share of GA P-charts and, I guess, so did djpil

Do keep in mind that this all predated the first of the microprocessor computers which came onto the market in the mid-70s - prior to that, if you could afford it, there was the odd TI bit of kit which allowed some number crunching capability. Needless to say, none of us had private access to the few mainframes around the place.

Spare a thought for us back then .. a computer (with a capability inferior to a modern pocket calculator, along with printers, cost me around $20k in the mid-70s but could we do things with that primitive kit compared to an old (still quite expensive) TI programmable calculator or slide rule. Would you believe I managed to upgrade the system several years later when a 5 kb hard drive came onto the market. (Maybe it was 5 mb .. whatever, it was tiny)

Cue Presidents of the USA ...

"We're not gonna make it"
"No no we're not gonna to make it"

I could well have sung this as I staggered out of Maitland Airport's runway 26 on a day well north of 40C in an old 6 cylinder 172 just shy of gross.

Somehow I drifted left to avoid old mates lounge window half way up the hill while observing the cushions on his couch. This was while planning on going under the power lines and performing a controlled crash up the slope in a clear area. While this was going on and in a state of sheer panic I somehow managed to glance at my mate next to me, intending to give him a crash brief only to discover he was engrossed in a magazine and completely oblivious to the situation. A serious slow motion event, he never did get the brief.

Somehow we made it over the hill, but it took several hours afterwards for me to regain composure and it was an event I will never forget.

Some aircraft should definitely be grounded at 40C.

Don't ask CASA, ask your Insurance Company, they will take greater interest in the ambient conditions should you fail to defy gravity.

It is in writing, in a letter attached to the most recent Vic RAPAC minutes.

We are not talking about a 747 or even a King Air where you probably do have performance data for every takeoff. The reality is, smaller aircraft are operated outside the parameters of the performance charts all the time, by necessity.

The C172 performance data goes to a density altitude of something like 12,000'. Why is it OK to operate at Mt Hotham at 35C, but not Mildura at 43C?

Density altitude was part of the PPL theory. You can in fact predict the effects with reasonable accuracy. CASA actually do that in the declared density charts. Maybe you just need to break the OAT and use the declared density?

The letter from CASA is actually claiming that the ranges specified in the performance charts forms part of the aircraft limitations. Which also suggests that the aircraft must be grounded below 0C.

I did some a little while ago at Point Cook using a video camera ...
https://www.casa.gov.au/files/vic170323pdf for that letter from CASA.
Want to do some more, JT?