CASA opinion: Aircraft must be grounded in temps over 40 degrees
Moderator
How do you feel about a "Normal Procedures" takeoff
In the first instance, quite obviously, I can't recommend it. However, for me, I don't have a problem for my takeoff and am comfortable that I can argue the toss were push to come to shove. In any case, I prefer to follow the POH data and OEM recommendations for light singles to avoid the problem.
If the POH doesn't have any data relating to a configuration/speed schedule, then the pilot is on his/her Pat Malone if choosing to operate in such a manner. If one isn't able to justify the activity, perhaps one ought to fly it as appropriate for whatever charts are extant ?
The big boys don't fly when it's over the limits I imagine their charts are compiled somewhat differently
The charts are more complex and cover considerably more concerns. However, at the end of the day, the two areas have their similarities
and they fly the chart speeds every takeoff and landing.
Indeed .. and I really can't see why the light aircraft can't be operated with a similar philosophy ?
Not to mention things like derated takeoffs that require more runway, V1 speeds etc. - they mean that the performance calculations are more critical.
All the numbers are critical if the operation be limiting. However, there is no a priori reason why data for the heavy need be more accurate than for the light .. other than the cost of development consideration.
and you find yourself consulting the charts
as one should, unless the data be the same as a previously determined case.
I would certainly be cautious about exceeding the temperature range.
Indeed, as would I.
What is the applicable rule? How is that rule applied to each parameter?
As we both know, there is none. Ergo, the second concern is moot. Equally, both you and I are able to generate a reasonable argument to cover reasonable excursions.
I probably ought to have kept my peace and not posted .... ?
Where do CASA's declared density altitude charts fit into all this, they don't mention temperature
I think they are an historical anachronism which hasn't yet been consigned WPB, round.
if an aircraft's AFM caps performance data at 40C
One ought to be VERY cautious when it comes to extrapolating temperatures .. OAT affects both airframe and engine and, in the absence of specific data relating to both, especially the engine, it can get rubbery .. quickly.
In the first instance, quite obviously, I can't recommend it. However, for me, I don't have a problem for my takeoff and am comfortable that I can argue the toss were push to come to shove. In any case, I prefer to follow the POH data and OEM recommendations for light singles to avoid the problem.
If the POH doesn't have any data relating to a configuration/speed schedule, then the pilot is on his/her Pat Malone if choosing to operate in such a manner. If one isn't able to justify the activity, perhaps one ought to fly it as appropriate for whatever charts are extant ?
The big boys don't fly when it's over the limits I imagine their charts are compiled somewhat differently
The charts are more complex and cover considerably more concerns. However, at the end of the day, the two areas have their similarities
and they fly the chart speeds every takeoff and landing.
Indeed .. and I really can't see why the light aircraft can't be operated with a similar philosophy ?
Not to mention things like derated takeoffs that require more runway, V1 speeds etc. - they mean that the performance calculations are more critical.
All the numbers are critical if the operation be limiting. However, there is no a priori reason why data for the heavy need be more accurate than for the light .. other than the cost of development consideration.
and you find yourself consulting the charts
as one should, unless the data be the same as a previously determined case.
I would certainly be cautious about exceeding the temperature range.
Indeed, as would I.
What is the applicable rule? How is that rule applied to each parameter?
As we both know, there is none. Ergo, the second concern is moot. Equally, both you and I are able to generate a reasonable argument to cover reasonable excursions.
I probably ought to have kept my peace and not posted .... ?
Where do CASA's declared density altitude charts fit into all this, they don't mention temperature
I think they are an historical anachronism which hasn't yet been consigned WPB, round.
if an aircraft's AFM caps performance data at 40C
One ought to be VERY cautious when it comes to extrapolating temperatures .. OAT affects both airframe and engine and, in the absence of specific data relating to both, especially the engine, it can get rubbery .. quickly.
This is one of those - sadly increasingly common - occasions where I wish I had the rest of my flying career (~20 years) behind me, not in front of me.
Join Date: Apr 2011
Location: Victoria
Posts: 750
Likes: 0
Received 0 Likes
on
0 Posts
Join Date: Apr 2011
Location: Victoria
Posts: 750
Likes: 0
Received 0 Likes
on
0 Posts
Arizona flights grounded as temperatures set to soar to 50C in extreme heatwave
Updated yesterday at 5:20pm
Arizona flights grounded as temperatures set to soar to 50C in extreme heatwave - ABC News (Australian Broadcasting Corporation)
Updated yesterday at 5:20pm
Arizona flights grounded as temperatures set to soar to 50C in extreme heatwave - ABC News (Australian Broadcasting Corporation)
Thread Starter
Join Date: Apr 2008
Location: Australia
Posts: 490
Likes: 0
Received 0 Likes
on
0 Posts
How do you feel about a "Normal Procedures" takeoff?
In the first instance, quite obviously, I can't recommend it.
In the first instance, quite obviously, I can't recommend it.
In any case, I prefer to follow the POH data and OEM recommendations
and they fly the chart speeds every takeoff and landing.
Indeed .. and I really can't see why the light aircraft can't be operated with a similar philosophy ?
Indeed .. and I really can't see why the light aircraft can't be operated with a similar philosophy ?
Cessna seems to have recognised that most of the time, the 172 will be flown off more than adequate runways.
When the is doubt about runway length, they assume that short field procedure will be used and that is what they use in the charts. But they do not recommend short field procedures for normal operations - the normal procedures presumably have more safety margin.
Cessna also seem to assume that pilots are smart enough to figure out when runway length might be an issue.
Where do CASA's declared density altitude charts fit into all this, they don't mention temperature?
I think they are an historical anachronism which hasn't yet been consigned WPB, round.
I think they are an historical anachronism which hasn't yet been consigned WPB, round.
One ought to be VERY cautious when it comes to extrapolating temperatures .. OAT affects both airframe and engine and, in the absence of specific data relating to both, especially the engine, it can get rubbery .. quickly.
Moderator
I'm not sure whether you're recommending flying the performance chart speeds or the recommended speeds? They are different.
Granted. If one doesn't have performance data, then there remains the problem of justifying the takeoff/landing post mishap. I am comfortable with both approaches but I have an appropriate engineering background to do some approximate sums to keep myself sweet.
Cessna seems to have recognised that most of the time, the 172 will be flown off more than adequate runways.
Aye, there's the rub. At what point does one perceive a problem ?
Cessna also seem to assume that pilots are smart enough to figure out when runway length might be an issue
One would hope that pilots are appropriately conservative so that such would be the case.
What temperature do you use for performance calculations when operating into a location without a forecast?
At present, the declared data is fine. Also, the BOM site data provides quite useful information. Apply whatever conservatively and, where feasible, carry an alternate to somewhere with forecast data. I really don't see a problem with this one.
(Guess it's not all that much different in principle to detailed software development work.)
Granted. If one doesn't have performance data, then there remains the problem of justifying the takeoff/landing post mishap. I am comfortable with both approaches but I have an appropriate engineering background to do some approximate sums to keep myself sweet.
Cessna seems to have recognised that most of the time, the 172 will be flown off more than adequate runways.
Aye, there's the rub. At what point does one perceive a problem ?
Cessna also seem to assume that pilots are smart enough to figure out when runway length might be an issue
One would hope that pilots are appropriately conservative so that such would be the case.
What temperature do you use for performance calculations when operating into a location without a forecast?
At present, the declared data is fine. Also, the BOM site data provides quite useful information. Apply whatever conservatively and, where feasible, carry an alternate to somewhere with forecast data. I really don't see a problem with this one.
(Guess it's not all that much different in principle to detailed software development work.)
Out of interest, I haven't read everything in this thread but note a lot of people choose the Common sense approach of extrapolating data for higher temps based on the data in the POH.
A lot of newer Aircraft seem to have a Temp Limit, when you extrapolate the Data though to beyond that Temp Limit the Aircraft could still perform when doing so, but there is still this limitation.
If you extrapolate beyond the data presented, how do you know for certain that it will perform?
When designing W&B Programs in the past using Excel for various Aircraft I've often noted that a lot of Aircraft don't follow simple extrapolation, they require complicated Polynomial Equations to be able to do so, something beyond I'd say the vast majority of Pilots and unless you evaluated the entire data set you would never be aware of it, how are you certain that beyond the 40 degrees performance data stated in your POH that Performance of the Aircraft wouldn't start to significantly decrease at say 45 degrees and beyond?
A lot of newer Aircraft seem to have a Temp Limit, when you extrapolate the Data though to beyond that Temp Limit the Aircraft could still perform when doing so, but there is still this limitation.
If you extrapolate beyond the data presented, how do you know for certain that it will perform?
When designing W&B Programs in the past using Excel for various Aircraft I've often noted that a lot of Aircraft don't follow simple extrapolation, they require complicated Polynomial Equations to be able to do so, something beyond I'd say the vast majority of Pilots and unless you evaluated the entire data set you would never be aware of it, how are you certain that beyond the 40 degrees performance data stated in your POH that Performance of the Aircraft wouldn't start to significantly decrease at say 45 degrees and beyond?
Moderator
lot of people choose the Common sense approach of extrapolating data for higher temps
.. if you don't have the engine data sets, in particular, you have not much idea at all of what happens at higher OATs other than presumptions based on general principles. Extrapolation into the higher OATs is not a routinely good idea, I suggest.
how are you certain that beyond the 40 degrees performance data stated in your POH
I would think one would have very little idea of what might happen.
Re the W&B considerations, I presume you are referring to the usual sloping limit lines on the weight x CG envelope ? They will only be first order there and, if one uses the weight x moment presentation, quadratic .. but, for a computer solution, why would you bother with the latter ? Not a big problem, I would have thought ?
.. if you don't have the engine data sets, in particular, you have not much idea at all of what happens at higher OATs other than presumptions based on general principles. Extrapolation into the higher OATs is not a routinely good idea, I suggest.
how are you certain that beyond the 40 degrees performance data stated in your POH
I would think one would have very little idea of what might happen.
Re the W&B considerations, I presume you are referring to the usual sloping limit lines on the weight x CG envelope ? They will only be first order there and, if one uses the weight x moment presentation, quadratic .. but, for a computer solution, why would you bother with the latter ? Not a big problem, I would have thought ?
In the Cessna 404 manual take off and landing tabulated data only goes to 40°C, however climb data, both dual and single engine, goes to 50°C.
How can we say 40 is the operational limit because the take off chart only goes that high, but climb data goes to 50?
I would have thought a prudent pilot would work backwards from the climb charts. Ensure s/he could reach the required gradient at temps between 40 and 50, and then from the take off chart determine the distance from a density altitude calculation.
All the Cessna manuals I've seen have a preamble to the performance section which says,
Notably the preamble also says the performance information allows planning with reasonable accuracy, not exact, as the preamble again says, it assumes "using average pilot technique (however you quantify that) with an airplane and engines in good condition". I don't see how using DA when temp is 40< to extract T/O data transgresses any rule, regulation etc The climb charts would suggest that 50°C is the practical limit, because that's as far as the chart goes. Why else have the climb charts go to 50 if take off is limited to 40? Inversion? Where do you source that data?
How can we say 40 is the operational limit because the take off chart only goes that high, but climb data goes to 50?
I would have thought a prudent pilot would work backwards from the climb charts. Ensure s/he could reach the required gradient at temps between 40 and 50, and then from the take off chart determine the distance from a density altitude calculation.
All the Cessna manuals I've seen have a preamble to the performance section which says,
Demonstrated Operating Temperature
Satisfactory engine cooling has been demonstrated for this airplane with an outside air temperature 23°C above standard. This is not to be considered as a operating limitation. Reference should be made to Section 2 for engine operating limitations.
Satisfactory engine cooling has been demonstrated for this airplane with an outside air temperature 23°C above standard. This is not to be considered as a operating limitation. Reference should be made to Section 2 for engine operating limitations.
john tullamarine, I should have been more specific, in a lot of my W&B Programs I've also included the ability for it to give you the TODR, LDR etc...etc..., was referring to those requiring Polynomials, not the CofG graphs and such. I agree entirely on your first point in response to my post.
megan, I understand what you're saying, but how do you know how the Aircraft will perform when above the 40degrees? You can extrapolate but you're assuming that the trend is continuous, perhaps after 40 degrees the Performance will decrease markedly?
I think we can all acknowledge that aircraft will have a temperature limitation, whether it's been put into your POH or not, it's common sense, eventually there has to be a temperature beyond which it's just not safe to be operating the Aircraft! Without the data showing this point how do you know where it is?
Most POHs/AFMs won't have it because, I'd suggest, they simply never tested it under extreme conditions above 40 degrees and therefore don't have the data. For all our fancy tech and know how it seems to be most of the information we have from our Manuals really came from someone jumping in the damned thing and taking it for a flight to figure out what will happen. I know it's more complicated than that but essentially that's what the data in them all boils down to.
I'm not saying that I necessarily agree with CASAs interpretation, BUT, I believe we all need to be reminded that if you choose to use your Aircraft without any proven data from the Manufacturer or another reliable source, you've basically just become a Test Pilot.
IMHO that really needs to be the biggest take away from this whole idea, extrapolation is fine and gives you a guide but you need to be prepared at some point to say "I don't know" when trying to decide if your Aircraft can comfortably and safely operate at such extreme temperatures and from there either seek the information from someone reliable who DOES know (Not just Joe Bloggs who has taken off tons of times at 45 degrees!), then if you can't get that data, perhaps it's time to sit back and wait for a few hours for things to cool off?
megan, I understand what you're saying, but how do you know how the Aircraft will perform when above the 40degrees? You can extrapolate but you're assuming that the trend is continuous, perhaps after 40 degrees the Performance will decrease markedly?
I think we can all acknowledge that aircraft will have a temperature limitation, whether it's been put into your POH or not, it's common sense, eventually there has to be a temperature beyond which it's just not safe to be operating the Aircraft! Without the data showing this point how do you know where it is?
Most POHs/AFMs won't have it because, I'd suggest, they simply never tested it under extreme conditions above 40 degrees and therefore don't have the data. For all our fancy tech and know how it seems to be most of the information we have from our Manuals really came from someone jumping in the damned thing and taking it for a flight to figure out what will happen. I know it's more complicated than that but essentially that's what the data in them all boils down to.
I'm not saying that I necessarily agree with CASAs interpretation, BUT, I believe we all need to be reminded that if you choose to use your Aircraft without any proven data from the Manufacturer or another reliable source, you've basically just become a Test Pilot.
IMHO that really needs to be the biggest take away from this whole idea, extrapolation is fine and gives you a guide but you need to be prepared at some point to say "I don't know" when trying to decide if your Aircraft can comfortably and safely operate at such extreme temperatures and from there either seek the information from someone reliable who DOES know (Not just Joe Bloggs who has taken off tons of times at 45 degrees!), then if you can't get that data, perhaps it's time to sit back and wait for a few hours for things to cool off?
but how do you know how the Aircraft will perform when above the 40degrees
Why have a chart giving the climb data to 50, if 40 is the limit for take off? Why would the manufacturer go to the expense of developing that climb data?
Edited to add: The SR22 take off data goes up to 50°C, and the preamble includes the note
For operation in outside air temperatures warmer than this table provides (50°C), use caution.
Last edited by megan; 22nd Jun 2017 at 18:17.
Moderator
I've also included the ability for it to give you the TODR, LDR etc...etc..., was referring to those requiring Polynomials
Without knowing what you have done in the past, I can only speculate. However, if one (as I suspect you are doing) intends to represent the physical charts by a computer implementation, there are three basic ways to go about it (with the test for acceptability being the delta between model and AFM data set .. not much in the way of linear data in the AFM)
(a) first principles .. too hard to figure the empiricals to get adequate accuracy so one leaves this for the OEM .. as in the EFB etc implementations these days
(b) polynomial regressions. Generally, too difficult to run multivariate regressions and achieve adequate accuracy so the usual way is to run single regressions for the printed lines and then either run interpolations or on the fly regressions for between line points .. great fun .. been there ... done that for a number of AFM data sets with very high accuracy albeit with the attendant boring slave labour to make it all work OK .. especially if the data set has numerous discontinuities .. painful. I presume this is the way you played with the stuff ?
Big potential for getting the fingers burnt with extrapolation, though, depending on the order of the the equation and what antics it produces in the extrapolated region where one doesn't have data points to constrain the regression .. one can guard against this but, in general, a risky business.
(c) interpolations, commonly splines. Useful for small data sets but I always preferred setting up the regression analyses and go from there.
how do you know how the Aircraft will perform when above the 40degrees?
The main concern is hidden discontinuities in the engine data pack. If you have some other data for the higher OATs, then you probably are reasonably safe with extrapolation unless there be some (strange) significant differences at the takeoff rating. Without such comfort, extrapolating the engine data is, at best, risky business ..
it seems to be most of the information we have from our Manuals really came from someone jumping in the damned thing and taking it for a flight to figure out what will happen.
That would be most unusual as the aim is to end up with something which can be used to model performance. Common practice is to model the performance and then use FT to sample test the accuracy of the model. Often it then becomes an iterative exercise to end up with an acceptable final accuracy in the model .. which then goes into the AFM data set.
We do know how the aircraft will perform in the climb up to 50°C, both dual and single engine
That is a useful source of comfort, I suspect.
Why have a chart giving the climb data to 50, if 40 is the limit for take off?
A question of limitation, then, becomes a legal question, rather than an engineering concern ?
Without knowing what you have done in the past, I can only speculate. However, if one (as I suspect you are doing) intends to represent the physical charts by a computer implementation, there are three basic ways to go about it (with the test for acceptability being the delta between model and AFM data set .. not much in the way of linear data in the AFM)
(a) first principles .. too hard to figure the empiricals to get adequate accuracy so one leaves this for the OEM .. as in the EFB etc implementations these days
(b) polynomial regressions. Generally, too difficult to run multivariate regressions and achieve adequate accuracy so the usual way is to run single regressions for the printed lines and then either run interpolations or on the fly regressions for between line points .. great fun .. been there ... done that for a number of AFM data sets with very high accuracy albeit with the attendant boring slave labour to make it all work OK .. especially if the data set has numerous discontinuities .. painful. I presume this is the way you played with the stuff ?
Big potential for getting the fingers burnt with extrapolation, though, depending on the order of the the equation and what antics it produces in the extrapolated region where one doesn't have data points to constrain the regression .. one can guard against this but, in general, a risky business.
(c) interpolations, commonly splines. Useful for small data sets but I always preferred setting up the regression analyses and go from there.
how do you know how the Aircraft will perform when above the 40degrees?
The main concern is hidden discontinuities in the engine data pack. If you have some other data for the higher OATs, then you probably are reasonably safe with extrapolation unless there be some (strange) significant differences at the takeoff rating. Without such comfort, extrapolating the engine data is, at best, risky business ..
it seems to be most of the information we have from our Manuals really came from someone jumping in the damned thing and taking it for a flight to figure out what will happen.
That would be most unusual as the aim is to end up with something which can be used to model performance. Common practice is to model the performance and then use FT to sample test the accuracy of the model. Often it then becomes an iterative exercise to end up with an acceptable final accuracy in the model .. which then goes into the AFM data set.
We do know how the aircraft will perform in the climb up to 50°C, both dual and single engine
That is a useful source of comfort, I suspect.
Why have a chart giving the climb data to 50, if 40 is the limit for take off?
A question of limitation, then, becomes a legal question, rather than an engineering concern ?
An answer from the horses mouth so to speak. I asked Cessna, Wichita, the following
Their reply
There is an argument in the community here as to whether the 40°C on the take off charts is a limit, or not.
ie: is take off permissible at temperatures in excess of 40°C.
I note in the 404 manual, dual and single engine, climb charts are provided for temperatures up to 50°C.
Do you consider the following an acceptable means of flight planning on the 404 when temperatures are in excess of 40°C and up to 50°C?
1. Determine from the climb charts the regulatory stipulated gradient.
2. Calculate the density altitude.
3. Determine from the take off chart a temperature and pressure altitude that gives the same density altitude.
For example, 50°C at zero pressure altitude the density altitude is 4,158 feet.
Entering the take off chart 1,000 feet pressure altitude at 40°C will give a density altitude of 4,210 feet.
4. Use the 1,000 feet PA, 40°C take off distance.
Is the same principal of using the density altitude to calculate take off distance when temperatures are above 40°C permissible, or is 40°C considered an operating limit for the singles (172, 207 etc)?
A view, which has currency in the community, is that you may not take off if the temperature is over 40°C.
ie: is take off permissible at temperatures in excess of 40°C.
I note in the 404 manual, dual and single engine, climb charts are provided for temperatures up to 50°C.
Do you consider the following an acceptable means of flight planning on the 404 when temperatures are in excess of 40°C and up to 50°C?
1. Determine from the climb charts the regulatory stipulated gradient.
2. Calculate the density altitude.
3. Determine from the take off chart a temperature and pressure altitude that gives the same density altitude.
For example, 50°C at zero pressure altitude the density altitude is 4,158 feet.
Entering the take off chart 1,000 feet pressure altitude at 40°C will give a density altitude of 4,210 feet.
4. Use the 1,000 feet PA, 40°C take off distance.
Is the same principal of using the density altitude to calculate take off distance when temperatures are above 40°C permissible, or is 40°C considered an operating limit for the singles (172, 207 etc)?
A view, which has currency in the community, is that you may not take off if the temperature is over 40°C.
The temperatures on the performance charts are provided to cover the majority of average operations. The temperature limits of these charts were not intended as a limitation for the aircraft, but simply what the aircraft was tested to. Simple interpolation as you have performed is appropriate.
Join Date: Apr 2008
Location: Australia
Posts: 669
Likes: 0
Received 0 Likes
on
0 Posts
In defence of Declared Conditions
Bravo, Megan 
Just a little word in defence of Declared Conditions: JT seemed to be implying that these should be headed for the bin, but I say:
What else can you use when planning your payload uplift from a place a few days, or weeks ahead of now? You obviously don't have ambient conditions, and I believe the regs stipulate that you must use the declared conditions.
Unlike probably 90% of Australian pilots, I have actually used them in anger, and can attest to their convenience.
Here is a great big hint to the people behind the NAIPS app for the iPad/iPhone:
Include the declared conditions in your app, somewhere. And while you are at it, get it to present the conditions not as a density altitude, but as a temperature and pressure altitude. That would be really good. Do it. Just do it.
Just a little word in defence of Declared Conditions: JT seemed to be implying that these should be headed for the bin, but I say:
What else can you use when planning your payload uplift from a place a few days, or weeks ahead of now? You obviously don't have ambient conditions, and I believe the regs stipulate that you must use the declared conditions.
Unlike probably 90% of Australian pilots, I have actually used them in anger, and can attest to their convenience.
Here is a great big hint to the people behind the NAIPS app for the iPad/iPhone:
Include the declared conditions in your app, somewhere. And while you are at it, get it to present the conditions not as a density altitude, but as a temperature and pressure altitude. That would be really good. Do it. Just do it.
The temperature limits of these charts were not intended as a limitation for the aircraft, but simply what the aircraft was tested to.
Join Date: Apr 1999
Posts: 56
Likes: 0
Received 0 Likes
on
0 Posts
It is interesting that this thread has concentrated on performance issues. In high or low temperatures the physical limits of the machinery can be of more concern than the performance.
All aircraft have environmental limits.
The Bell 206L3 has a max ambient air temp of 51.7c (125F) and I can say from first hand experience flying in temps around this limit has one concerned about Gearbox temps/oil temps etc.
The R22 has a stated demonstrated limit of 38C at sea level due to cooling issues. Again first hand experience of oil temp on red line when operating a standard R22 in the tropics. Look at R22s used for mustering and you will notice they have been fitted with a larger oil cooler to aleviate some of the problem. What are these high ambient temps doing to other lubricated components.
Take off performance may be the least of the issues of operating in high ambient temps.
All aircraft have environmental limits.
The Bell 206L3 has a max ambient air temp of 51.7c (125F) and I can say from first hand experience flying in temps around this limit has one concerned about Gearbox temps/oil temps etc.
The R22 has a stated demonstrated limit of 38C at sea level due to cooling issues. Again first hand experience of oil temp on red line when operating a standard R22 in the tropics. Look at R22s used for mustering and you will notice they have been fitted with a larger oil cooler to aleviate some of the problem. What are these high ambient temps doing to other lubricated components.
Take off performance may be the least of the issues of operating in high ambient temps.
Take off performance may be the least of the issues of operating in high ambient temps
Satisfactory engine cooling has been demonstrated for this airplane with an outside air temperature 23°C (41°F) above standard. This is not to be considered as an operating limitation. Reference should be made to Section 2 for engine operating limitations.