Flying jab's over 40 degrees

[Ross]

Back on topic of temperature to stop flying of 40 degrees C at MTOW as quoted for the Jabiru J160 and the Jab LSA-55 in their respective POHs.

 

A possible extra consideration besides the A/C structure might be the upper limit for engine oil temperature. If the ambient temp is high enough the engine cooling system may not be able to keep the oil temp low enough to keep oil oxidation down to a practical level thus producing rapid engine failure.

 

 

[poteroo]

Daylight saving has been the saviour of our J160. It's cool for an extra hour in the mornings now, so we make great use of that extra revenue hour. Thank you pollies, one & all, for solving our Jabby 'overheating' dilemna!

 

happy days,

 

 

[Dieselten]

A couple of days ago I had the occasion to fly a J160 from Wollongong to Nowra (YSNW) and return. On takeoff at YWOL the OAT was 34 degrees, and at 2500 feet it was 36. Oil temperatures went to the 100 degree mark and stabilised there. According to the Garmin 296 when we plugged all the data in, the DA was 4661 feet, and YWOL is only 32ft amsl!

 

We cruised to YSNW at 2500 feet to take advantage of nearly 30kts of hot tailwind. Having done a weather-flight earlier in the day I knew it got hotter the higher you went, so we we elected to maintain 2500ft for the trip.

 

Departure from YSNW saw the OAT (measured by a probe in the wing-root fairing, shaded but in slowly circulating air) at 38 degrees...right on the max temp as advised in the a/c operating manual. With a crew of 2 and approx 70l fuel we used first-stage flaps (20deg) and got a pretty normal takeoff run and cruise-climbed at 80KIAS until we reached 1500ft in an OAT of 36 deg. During the cruise-climb the oil temp went to the top of the green arc and stabilised there.

 

There was no cool air, and apparently freezing-level for the day was somewhere near 12,000 feet! The sea-breeze was hot, and not wishing to battle a 30kt headwind we stayed at 1500ft all the way back where we battled a 23kt headwind instead. Oil temps were monitored carefully throughout and never went into the red, but they were at the top of the green until we commenced speed reduction in the YWOL circuit before extending flaps.

 

OAT on the ground at YWOL was a relatively comfortable 34, and during taxi after clearing the runway we observed the oil temps well back into the green.

 

I had no concerns about structural issues, but I watched those oil temps like a hawk all the way back. We managed a cruise TAS of just on 100kts (by Garmin 296), but I really wouldn't like to fly the J160 above 38 degrees OAT due to the real potential for oil temps to get out of the comfort-zone. Toasting your oil (and engine) has little to recommend it.

 

I'm thinking of dropping the oil out ASAP in case it's been "aged" pematurely. Oil is cheap.

 

 

[Guest Rocko]

Sometimes, I think common sense goes out the window.

 

Let me see if I have this right.

 

All Jabiru aircraft, apart from the J120, state a Max OAT at 38-40C (whatever it says!)

 

They're all made from the same material.

 

So, why would the J120 be any different?

 

When I bought my Xair, the manuals (including both operating AND assembly manuals) had a few....errors. Quite a few, in fact.

 

I had since found 3 different flight manuals, for the same aircraft, with slightly different information. One of these (the one included with my aircraft) included the stall speeds being listed in an incorrect order.

 

So, would this mean, because of a typo, that the stall speed is lower for 2 steps of flaps and not 3? Should I fly it this way?

 

Common sense!

 

At the very least, given it's a relatively new aircraft, if I noted, or was susequently made aware of, such an omission in the J120 manual, the first thing that would scream to me would be "Manual malfunction". I'd be interested to see whether the information is then included in future editions of the manual.

 

As far as not being able to "prove" what the outside air temp was at a crash site, I'd be pretty sure an insurance company, or the RAA, would not have any particular problem getting some fairly hard facts from the BOM, as to the expected OAT in the area. Good luck to anyone proving otherwise, to an insurance company.

 

I keep wondering why we so often see these discussions move to ways to justify how we can fly outside the allowed envelope, rather than just accepting the facts for what they are. The temps state 38-40C. Flying outside it is illegal. Do so at your own (and your Px) peril! Wasting breath justifying it is like trying to justify driving at 120KPH in a 100 zone. Sure, your car will handle it. Sure, you can probably do it safely. However, that doesn't make it legal. Nor does it make it all that "bright". So, why try and justify it?:hittinghead:

 

 

[Guest Rocko]

Just out of curiousity, is there a minimum operating OAT for the Jabiru?

 

 

[quentas]

Just out of curiousity, is there a minimum operating OAT for the Jabiru?

That would be when they wont start..inbuilt protection from the cold..

 

 

[facthunter]

Cold air.

 

The coldest temp I can recall operating at is minus 56 degrees C. You start to wonder how brittle some substances are at those temps. Nev.

 

 

[Steve Donald]

Sometimes, I think common sense goes out the window.Let me see if I have this right.

All Jabiru aircraft, apart from the J120, state a Max OAT at 38-40C (whatever it says!)

 

They're all made from the same material.

 

So, why would the J120 be any different?

 

When I bought my Xair, the manuals (including both operating AND assembly manuals) had a few....errors. Quite a few, in fact.

 

I had since found 3 different flight manuals, for the same aircraft, with slightly different information. One of these (the one included with my aircraft) included the stall speeds being listed in an incorrect order.

 

So, would this mean, because of a typo, that the stall speed is lower for 2 steps of flaps and not 3? Should I fly it this way?

 

Common sense!

 

At the very least, given it's a relatively new aircraft, if I noted, or was susequently made aware of, such an omission in the J120 manual, the first thing that would scream to me would be "Manual malfunction". I'd be interested to see whether the information is then included in future editions of the manual.

 

As far as not being able to "prove" what the outside air temp was at a crash site, I'd be pretty sure an insurance company, or the RAA, would not have any particular problem getting some fairly hard facts from the BOM, as to the expected OAT in the area. Good luck to anyone proving otherwise, to an insurance company.

 

I keep wondering why we so often see these discussions move to ways to justify how we can fly outside the allowed envelope, rather than just accepting the facts for what they are. The temps state 38-40C. Flying outside it is illegal. Do so at your own (and your Px) peril! Wasting breath justifying it is like trying to justify driving at 120KPH in a 100 zone. Sure, your car will handle it. Sure, you can probably do it safely. However, that doesn't make it legal. Nor does it make it all that "bright". So, why try and justify it?:hittinghead:

Hello Rocko, after the initial raised topic i contacted the Manufacturer as did the administrator, there are no omissions from the flight manual as it is LSA and no the wing is different from the others as well being solid foam core.

As to the other models they are tested to 54deg c at 9g's for certification, the manufacturer stated this is where the resin starts to soften, but after about 3 years this temp raises to about 70 deg the structure actually becomes stronger,this was explained to other parties who also spoke to the Manufacturer, any concerns should really be made to the manufacturer so a detailed explanation can be offered and answer any question accurately, apparently the certification process of the other models dictates the 38deg limit on those particular aircraft and the composite aircraft has to exceed the limitations of structural integrity than does a metal aircraft, under the current certification process and are proven statically and physically to destruction including being placed in a propane furnace and load tested in the presence of a CASA Official. So you can see the structures meet a very high standard of compliance, yet aircraft from overseas are omitted from this and accepted with the certification from their place of origin using whatever certification process that may occur in that country.

 

i also have an OAT probe fitted but have never seen temps outside in cruise that come anywhere near problematic or breaching of rule's. I do recomend any concerns anyone has to speak to Jabiru direct about their Aircraft, they are very happy to do so and are completely transparent with all information re their products.

 

 

[Ultralights]

The coldest temp I can recall operating at is minus 56 degrees C. You start to wonder how brittle some substances are at those temps. Nev

thats one thing no one has been able to answer for me, working at Qantas, i was a structural engineer, specialising in composites, now on a standard 747-400, there is a large amount of fibreglass and carbon fibre, all flight control surfaces, all the wing to body fairings, spoilers, leading edge slats and krugar variable camber flaps, and half the vertical stabiliser and horizontal stabiliser, are all made of composite materials, not to mention, all the engine cowls, internal cowlings, and thrust reverser blocker doors.

 

now, according to the boeing repair manuals, to seperate the bonded components, for repais, the general procedure is to cold soak the component in dry ice, when its at the same temp as dry ice, then we break it apart with surprisingly little force... now, when these parts are in service, they are cold soaked at below -50C for 12 hrs at a time or longer! yet funnily enough, still maintain most if not all their properties.

 

as for the Jabiru, i wouldnt worry to much about a 40deg day, they are built using polyester resins, which as a general rule, will hold their design properties up until 70 deg c. Epoxies usually the same, anotehr genral rule is the best cure temps is usually the temp i will begin to loose its designed properties, so a 70Deg general purpose resin will start to soften at about 70 deg, if its autoclaved to 1000 deg, then 1000 deg will be the point it starts to loose strength... though this is a general rule only..

 

but, if the Jabiru in 40 deg heat was painted black, then the surface of the resin will quite easily reach the best cure temps.

 

as stated before, i think the reason a jab is limted to 40 deg, is that the density atl at those temps will fast approach the aircraft ceiling height.. eg, 34 deg at Wollongong, gave a desity alt of over 4000 ft! with those conditions, but at 40 deg, im sure the density alt will be well up over 5000 ft if not approaching 10,000

 

 

[Guest Rocko]

Fair enough, that. Nice to see an actual factory reference.

 

 

[Ben Longden]

Perhaps the first thing to check would be NAIPS... if it has those magic words "severe turbulence" and an altitude..

 

Thats the first thing.

 

The second thing is just how warm the cabin is going to be... if the planes been parked in the sun, then it will be 70+ inside.

 

Both are certain to make a trip unpleasent..

 

Ben

 

 

[bilby54]

I wonder if Bruit2 has got an acceptable answer from all of this?

 

I would suggest that the other part of the matter is the calculation of pressure height. Flight manuals seem to be the most disorganised reads ever published and some 'stuff' can be real hard to find in them.

 

The SP 470 gives an actual a take off distance increase of 115 metres for every 1000' of pressure altitude. Not a huge problem on a strip with a long runway but if it is the usual bush strip that you flew into in the morning for a social outing and you decide to leave in the afternoon when the temps are up.....

 

Temperature has a huge bearing on pressure height and 40 deg is equivalent to 3000' apparent increase in airfield height so add 345 metres to the take off distance required. It also happens on landing.

 

I have have attended a few incidents where an aircraft has gone through the fence purely due to PH. The other point that was mentioned earlier is the performance of the pilot in hot conditions and their ability to react in eventfull situations.

 

The over riding factor in all of this is SAFETY and Motz and others, were right in saying that it is good airmanship to stick with the book.

 

Just for the record, I flew for many years in the desert parts of this country too:laugh:

 

 

[Burlc]

So what about those of us who live in the Northwest on Northern Territory.

 

The temperture here is over 38 regularly 10 months of the year plus with the added humidity that goes with it.

 

I know of 1 Jabiru owner based in YPPD and a J230,J120 based at Darwin.

 

I am sure Jabiru was'nt concerned when they sold these aeroplanes to these customers knowing the operating conditions they would be used in.

 

Thats my 2 cents worth.

 

 

[Vorticity]

I think Bilby might have just re-asked what the original question was. How do the Jabiru perfrom when it is hot? (I avoid a certain temp having read the many worthwhile discussions before hand!).

 

If you go flying on a hot day in a Jab are you going to be white knuckled watching the other end fence coming at you?

 

I am looking around at an aircraft to take to Darwin. The Jab is on my list. This thread, in spite of some of the attitude early on, has been extremely interesting:thumb_up:

 

 

[Captain]

My experience with a 160 & a 230 is that the performance of the Jabiru wing does not drop any more than any other aircraft as the temps go up around 40C.

 

I reckon that they fly just fine in the hot weather around here.

 

Oil temp is also OK at these temps, in my experience, as long as you get away in reasonable time and go to a fast climb once the flaps are away (90 - 100 knots in the 230) to encourage good airflow thru the oil cooler. Still climbs at 500 - 700 fpm at those speeds on a hot day.

 

No worries.

 

 

[shafto]

Hey all

 

After reading through all three pages I've decided to make this my first post! Woo

 

SO im not a flyer (yet:thumb_up:), but am a budding engineer.

 

Now after reading though manuals, pilot and aircraft specific Ive come up with this, now of course the PIC decideds weather to fly or not regardless of what the manual says, so ill let you guys decide.

 

After reading through the Pilot Manual of the J160, i obviously came across the section where is states the section where it says 38c is max OAT. After looking at the Takeoff Config Matrix i did some rough calculations to give estimates as to how the aircraft will perform. Unlike some earlier posts, the reason there is the temp range is because of aircraft performance, not the composites failing.

 

OK so here are the assumptions the matrix is your in a take off config, with 68 KIAS. So easily you can see at 38c OAT and at SEA LEVEL climb rate at MTOW is 461ft/min. Extrapolating that out you can assume that you would loose around 120ft/min climb for every increase of 20 degress. So you could expect a climb rate of around 320-360 ft/min. I wouldnt like to think what the climb rate would be if you got even the slightest down draft.

 

Also have a quick look at take of distance needed, I've put that table up as well, give yourself a rough idea how much more runway you will need to even get in the air.

 

How about a quick look at how the engine performs so you can all see the power loss. I used The Bureau of Meteorology's annual national average of relative humidity, the east coast is 70% and west coast 60% to 70%...so I'll just say 70% relative humidty (RH) for arguments sake.

 

Jabiru 2200 at 52 degrees at sea level with 70% RH; the relative HP is 85.7% of 80HP or 68.57 HP. Now thats at sea level. Its only going down as altitude increases as well.

 

Jabiru 3300 at 52 degrees at sea level with 70% RH; the relative HP is 85.7% of 120HP or 102HP, again its only going to go down. You will not regain HP performance by going higher.

 

Anyway there are the reason's why there is a max temp. Now personally I agree with the people that have said if you operate out of the Operating Handbook you are operating illegally. Imagine you did crash you didnt have climb rate, and hit a tree, you killed your best friend and you survived. The court case begins, the judge asks you under what bases you operated outside the book. Your only defense is Old mate Jabiru said you could fly it to 52 degrees. Guess what? old mate jabiru will convinenlty forget he said you could operate it at that temperature. All he has to say is you should have read the manual.

 

The final nail in the coffin is the warning above the takeoff distance matrix, and i quote "Extrapolation outside the boundaries of the Take-Off Distance Table is not permitted. When the outside air temperature and/or pressure height is below the lowest range included in the table, the aircraft performance shall be assumed to be no better than that appropriate to this lowest Jabiru Aircraft range. The performance information is not valid when the outside air temperature and/or

 

pressure height exceeds the maximum values for which this information is scheduled." (Jabiru J160-C Pilot Operating Manual Page 5-4 Rev 21 Dec 2005)

 

Actually that quote is used on all performance tables. Take off performances, landing distances, everything

 

So the answer is yeah sure you can fly in 52 degree heat; you could fly it at 70 degrees if it got that hot, you can even fly a plane without a licence too if you want. But as a consientious pilot you should know your climb rate is greatly reduced, and thats the least of your problems. As soon as you operate outside the manual, if anything goes wrong you are resposible for the lives you damage.

 

 

 

 

[LEJ]

Hi shafto,

 

Thanks for the insight. That was truly an eye opener for me.

 

 

[shafto]

No probs LEJ, it looked like there was a fair bit of confusion out there! Hopefully people will understand what the issue is, and it has nothing to do with composites failing. Or atleast thats the least of your problems!