5100 Jabiru in a factory built Jabiru.

[gofastclint]

Has anyone installed a Jabiru 5100 in a Jabiru aircraft? Just curious. Think it would make a nice hot rod aircraft. I see there is ample room under the engine cowling of a J160, match that with a decent prop and mount some things farther back to get the weight right. Be good on short runways. The first all Aussie muscle plane lol. Just for fun of course.

 

 

[Guest brentc]

You'll find that there won't be enough room under the cowls in the J160 as to fit a 6 cylinder 3300 in there there is a new set of cowls so to fit an 8 you'll need even bigger ones. It's an interesting idea, but unless VNE was increased there would be little point other than for a spectacularly short takeoff and super fast climb.

 

 

[gofastclint]

You'll find that there won't be enough room under the cowls in the J160 as to fit a 6 cylinder 3300 in there there is a new set of cowls so to fit an 8 you'll need even bigger ones. It's an interesting idea, but unless VNE was increased there would be little point other than for a spectacularly short takeoff and super fast climb.

Cheers BC, Just out of curiosity what is the first factor of the VNE on the Jabiru? Alot of planes start with vibration.

 

 

[Tomo]

Cheers BC, Just out of curiosity what is the first factor of the VNE on the Jabiru? Alot of planes start with vibration.

The needle moves into or past the red....

 

:hittinghead:

 

 

[gofastclint]

The needle moves into or past the red....:hittinghead:

Ha Ha Ha Ha Ha!

 

 

[Ultralights]

the 8 cyl in the J230/450 would make it a fantastic performer!

 

 

[gofastclint]

It does seem a little funny that they don't fit it into a 230, especially with the financial crisis affecting GA so much, it would be a great alternative to a cessna 182 or one of those other GA planes.

 

 

[BLA82]

It does seem a little funny that they don't fit it into a 230, especially with the financial crisis affecting GA so much,

Whats the difference between GA and RA-AUS it is affecting everybody

 

 

[gofastclint]

Whats the difference between GA and RA-AUS it is affecting everybody

Because generally GA planes have much higher operating and maintenance costs. So going to a smaller aircraft will save you money.

 

 

[BLA82]

Because generally GA planes have much higher operating and maintenance costs. So going to a smaller aircraft will save you money.

Fair comment but I think putting an 8cyl in a Jabiru is just a bit past the recreational/small aircraft idea:off topic:

 

 

[Guest brentc]

It does seem a little funny that they don't fit it into a 230, especially with the financial crisis affecting GA so much, it would be a great alternative to a cessna 182 or one of those other GA planes.

I'm not sure what the limiting factor is for VNE on the Jab.

 

In some small Jabs getting near VNE can become very uncomfortable and bounce you around quite a bit. In a J170 I literally had the wing flapping at 110 knots! (problem with aileron)

 

My J400 seems happy at or over VNE however I run out of trim and require much forward input to keep the nose level, plus my ailerons become very stiff and hard to roll the aircraft., which is a symptom of my aircraft anyway.

 

 

[gofastclint]

So I guess the high speed cruise is out, and if the configuration was built a tow plane would be its only real use.

 

 

[Guest Flyer40]

A big engine can make good sense in terms of efficiency. I just read about a Bearhawk with an O540 in place of the more usual O360. This aircraft also has a modest Vne but the big engine gives incredible STOL capability and in cruise it's throttled way back to 19 squared (about 40%) where it turns the same cruise speed as the 360 but does it on much less fuel than the 4 cylinder.

 

Wonder how much a 5100 powered J400 would consume at normal cruise speed?

 

 

[Yenn]

Could you really compare a J230 with a Cessna 182?

 

In my opinion the C182 is more like a truck and the J230 a Toyota Camry. Built for entirely different uses.

 

 

[gofastclint]

A big engine can make good sense in terms of efficiency. I just read about a Bearhawk with an O540 in place of the more usual O360. This aircraft also has a modest Vne but the big engine gives incredible STOL capability and in cruise it's throttled way back to 19 squared (about 40%) where it turns the same cruise speed as the 360 but does it on much less fuel than the 4 cylinder.Wonder how much a 5100 powered J400 would consume at normal cruise speed?

Thats an interesting one. There is not much data on the 5100, I've never even seen one in the flesh.

 

I'm already dreaming of a MoTeC Duel EMS with EFI and a redundant fuel delivery system.

 

 

[Guest Flyer40]

Could you really compare a J230 with a Cessna 182?In my opinion the C182 is more like a truck and the J230 a Toyota Camry. Built for entirely different uses.

Depends on your point of reference. To me the 182 is the safest and most comfortable way to travel with the family. Stable ride, luxurious seats, airbags for safety, more information than I can poke a stick at, and an amazing auto pilot. Certainly not truck-like. I'd be more inclined to compare it to a 5 series bee em. But I agree, certainly very different to a J230.

 

Anyway

 

 

[skeptic36]

I'm not sure what the limiting factor is for VNE on the Jab.

My J400 seems happy at or over VNE

 

Um what does VNE stand for exactly ?

[gofastclint]

I'm not sure what the limiting factor is for VNE on the Jab.

My J400 seems happy at or over VNE

 

Um what does VNE stand for exactly ?

Very Naughty Elephant

 

[Guest brentc]

VNE - Velocity Never Exceed speed. It's red-line on the Airspeed Indicator and the speed that you don't go over in any conditions. Any higher and you run the risk of structural failure etc. It's not uncommon to exceed VNE if you are playing around and are not careful and I'm quite sure that there is some margin in there from the designer, however it would be unwise to partake in such flying if avoidable.

 

 

[Guest pelorus32]

Um what does VNE stand for exactly ?

As others have said it stands for Velocity Never Exceed. And it means exactly what it says.

 

From talking to those who have witnessed the death of pilots due to exceeding Vne I can tell you it is something that stays with them for ever.

 

DO NOT assume that someone else has put "safety factors" into the Vne number. Put your own safety factors in there.

 

If your a/c is going to behave badly above Vne - particularly if it is going to flutter, you will have NO time to do anything about it. The development and the end result of flutter are very fast and very terminal.

 

Last year (or perhaps the year before) there was a very good article about the dangers of excessive speed in the RAAus Mag. The opening of that article was an email from a friend to me just after he had witnessed the death of another friend whilst doing a low pass in excess of Vne. The aircraft "exploded" at 150 metres above the ground.

 

Makes you shudder to think.

 

Regards

 

Mike

 

 

[Guest brentc]

The frustrating part of witnessing such an event is that the act of exceeding VNE in this instance is completely wasted. The on-the-ground observer (particularly a non-aviation type), is not going to notice if the low pass happens 10-20 knots less because the pilot is keeping under the VNE speed. Same goes with the Christmas Day beat-up in a 172 hitting power lines. Had he been 20 or even 50 feet higher, it would still have been an entertaining site for those non-aviation types on the ground.

 

Completely avoidable fatalities.

 

 

[gofastclint]

When it comes to flying, just don't push your planes limits. Even the air race planes operate within their design limits. Dying isn't fun.

 

 

[Guest Andys@coffs]

the 8 cyl in the J230/450 would make it a fantastic performer!

Hmmm I admit to some bias....I think the 230 as is is already a fantastic performer, perhaps there was an issue with being hit with an ugly stick, but realistically to travel at 120kts true cruise, carrying as much as it can carry(VH of course...) , on 22lts/hr is already reasons to claim "fantastic"

 

Andy

 

 

[Guest Andys@coffs]

A big engine can make good sense in terms of efficiency. I just read about a Bearhawk with an O540 in place of the more usual O360. This aircraft also has a modest Vne but the big engine gives incredible STOL capability and in cruise it's throttled way back to 19 squared (about 40%) where it turns the same cruise speed as the 360 but does it on much less fuel than the 4 cylinder.Wonder how much a 5100 powered J400 would consume at normal cruise speed?

Now thats an interesting comment that in the context of a 5100 needs more debate. On my 6cyl jab, Im told to cruise with RPM at 2850. to cruise with much lower RPM which is underutilising the available power causes damage to the engine Im told through Jabiru and will result in a shorter operating life.

 

If the 5100 cant be utilised at cruise within its defined cruise operating RPM range then in addition to fantastic climb, unbelievably short take off you'll also get unbeliveably low engine life and unbelieveably expensive cost per hr. In addition, because you cant easily increase fuel capacity or VNE you also get reduced range. Personally (and I claim no mechanical engineering education) I cant see how having to provide energy to overcome the additional friction of 2 more cylinders can be done for less fuel than driving the 6 cyl would need. In level flight, cooling issues aside, I can easily drive the J230 up to VNE without running out of throttle so its not like there is even any need for more hp that I can see?

 

Am I missing something?

 

Andy

 

 

[Guest Flyer40]

Andy, can you add more info about how operating at a lower rpm reduces the life of the Jab engine. It sounds counter intuitive, I'd like to know their reasoning.

 

As for bigger engine efficiency, the article I mentioned earlier stated that the big engine uses 7.5 gallons an hour while the 360 in the same airframe uses 9 gallons an hour. I'm not an engineer but I'll have a go at why I think it works:

 

Assume both engines have a volumetric efficiency of about 80%. In the Bearhawk the 540 cruises at 40% power, the 360 at 75%.

 

The O540 will theoretically consume 432 ci of fuel/air gas per revolution at sea level at full throttle, which at cruising rpm of 1900 is 820,800 ci of gas per minute.

 

The O360 will theoretically consume 288 ci of fuel/air gas per revolution at sea level at full throttle, which at cruising rpm of 2300 is 662,400 ci of gas per minute.

 

At this stage of the calculation the 4 cylinder engine looks more economical. But I'm guessing the 360 would be at or near full throttle to maintain 2300 rpm with a constant speed prop. Whereas the 540 would be throttled back somewhat. And that's where the big engine gains its advantage.

 

I don't know how to do the next part of the calculation but for the sake of illustration, 40% of the 540's maximum possible fuel/air gas consumption at 1900 rpm is 328,320 ci per minute. Taking 75% of the 360's max at 2300 rpm we consume 496,800 ci of gas per minute.

 

So for the same cruise speed the big engine uses 168,480 ci less fuel/air gas per minute.

 

There are obviously a lot of other variables which I deliberately left out because I'm illustrating a concept, not performing an engineering analysis.

 

If I were to think of an analogy it would be the V8 engined car that uses less fuel on a long highway journey than a 4 cylinder car.