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.