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Hi everyone

 

I was just doing a desktop comparison between the Jabiru J160 and J170. One of the things that got my attention was the difference in stall speeds between the 2 aircrafts. The clean stall speed of J160 is 55KCAS (58KIAS), whereas that of the J170 is 45 KCAS. A difference of 10 knots!!

 

Just wondering if this raises any eyebrows or is it a cause for concern, as it appears to have a very low threshold or safety margin, before it can enter a stall or spin, especially if one happens to do a steep turn and if the speed was to bleed off rapidly and unintentionally. 

 

I would like to know of any real life experience or any thoughts on this high stall speed in a J160?

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Assuming those speeds are correct, this problem would only occur IF you got from one plane to another and just flew it as if it was the same plane. Variations occur due loading , density altitude and such as well as individual planes . Across the Cessna hi wing range there are LARGE variations. You carry a margin  above the stall speed (whatever it is) suitable for the circumstances. Gusts, manouvering  etc. You should be able to  fly any U/L without an airspeed Indicator SAFELY even if not right on the correct speeds with a bit of practice. Higher speed would be appropriate as safety demands you err on the SAFE side..   IF you ever get where there's issues with the planes handling and or Instrument indications fly it at a safe height and check if it's normal in manouvering and if it's not, determine by experiment what procedure would be best to make the approach as safe as possible. The normal POWER and ATTITUDE with the plane configured properly undamaged or altered should produce the same SPEED.. Nev

Edited by facthunter
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careful not to confuse IAS and CAS numbers

 

there is considerable departure between IAS and CAS at low airspeeds in those birds.

 

the J160 doesnt have as much wing.  so, drag will also be lower, also. Most people love their J160 compared to J170.  a sports car.

 

J160D is full flap stall = 45 KCAS (48 KIAS) . clean is 55KCAS (58 KIAS). But remember, depending on alot.... like if the prop is turning etc,

J160C is similar. 

 

In the jabs you do get alot of liberties near the stall. My J230D still wants to fly at below the book stall speed @ MTOW..... clean or flaps full.

 

It will also be a few knots either way depending on if the plane is full of bugs or not.  

 

The Jab book figures take into account variations between aircraft, so usually worst case numbers.

glen.

 

 

 

Edited by RFguy
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1 hour ago, anjum_jabiru said:

Hi everyone

 

I was just doing a desktop comparison between the Jabiru J160 and J170. One of the things that got my attention was the difference in stall speeds between the 2 aircrafts. The clean stall speed of J160 is 55KCAS (58KIAS), whereas that of the J170 is 45 KCAS. A difference of 10 knots!!

 

Just wondering if this raises any eyebrows or is it a cause for concern, as it appears to have a very low threshold or safety margin, before it can enter a stall or spin, especially if one happens to do a steep turn and if the speed was to bleed off rapidly and unintentionally. 

 

I would like to know of any real life experience or any thoughts on this high stall speed in a J160?

Where did that info come from? It's wrong! When I learnt to fly the Jabs it was in a J160 and my speed on late final was around 60kts. I think you'll find 45kts clean and 40kts with full flaps. (10 minutes later....) I downloaded the POH for the J160D and it does state what you said. That's very strange, I'd be tempted to contact Jabiru.

Edited by Jabiru7252
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spacesailor-  its a different wing size, different MTOW, different tail .....  yes higher wing loading. different flaps to full airfoil ratio......

 

Like I said  in my comment- Jabs usually fly pretty well  around their stall, at least when flying straight..... and the book numbers are worst case taking into account variation between aircraft

 

anjum_jabiru - I think most people would agree with me, that airspeed does NOT bleed of rapidly in the Jab, they have a very slippery airframe AND a wing that has a very low induced drag increase  at low airspeeds.

And, I'd have to ask, what are you doing flying down around 50 knots without some flap out? anyway, I am sure some J160 owners will pipe up. 

 

Edited by RFguy
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Thanks guys. All your replies are so informative and helpful. It all makes sense. Just don't fly it below 70 knots, no steep turns below 80 knots, and limiting to 30' bank angle if flying between 70 to 80 knots, as in base to final or crosswind turn, I guess should be OK.

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You should be able to handle 45° turns without a worry at those speeds. You might need them when trying to get down between trees into a clearing during a forced landing. Go out and try some steep turns at slower speeds with plenty of height just to see how things feel. 

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Go find a school that has J160s (there are plenty of them) and go up high with an instructor and see how she performs.  I think you will be surprised.

 

Also, I think your numbers are a bit unqualified. For example, the plane may be just fine in say a 70 kts 60 deg bank if it is in a steep descending turn where energy is being replenished by gravity and airspeed can be maintained.....  No problem there.  And if you choose never to fly less than 70 kts, it will never land.

 

Respectfully, maybe get more flying experience and / or work with an experienced instructor before coming to any conclusions.
 

Edited by RFguy
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15 hours ago, anjum_jabiru said:

Hi everyone

 

I was just doing a desktop comparison between the Jabiru J160 and J170. One of the things that got my attention was the difference in stall speeds between the 2 aircrafts. The clean stall speed of J160 is 55KCAS (58KIAS), whereas that of the J170 is 45 KCAS. A difference of 10 knots!!

 

Just wondering if this raises any eyebrows or is it a cause for concern, as it appears to have a very low threshold or safety margin, before it can enter a stall or spin, especially if one happens to do a steep turn and if the speed was to bleed off rapidly and unintentionally. 

 

I would like to know of any real life experience or any thoughts on this high stall speed in a J160?

Anjum - I am trying very hard to resist the temptation to promote a certain aircraft manufacturers products (for fear of being abused)- the stall speeds you quote are a good 15 +knots higher - scary in a LSA!

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Just now, skippydiesel said:

Anjum - I am trying very hard to resist the temptation to promote a certain aircraft manufacturers products (for fear of being abused)- the stall speeds you quote are a good 15 +knots higher - scary in a LSA!

Hey Skippy how fast were you going in your 27knot stall machine when you stalled? short of the runway?. I don't feel scared when piloting my 54knot full flap stall Beech23🤔🤔.

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Hi Skippy, nice to hear from someone at The Oaks! I did my flying lessons in a Jab LSA up there. In fact I was contemplating between going with the J170 up at The Oaks or the J160 at Albion Park, given the scary figures for stall speed for the J160. I was flying the Pipistrel Alpha Trainer at Albion Park, which is a fantastic little airplane.  Although the Jabs had got a bad rap, for their engine failures, statistically, the commonest cause of fatal accidents is pilot error. And given the really low number of fatalities in a Jab, I would not wish to be in anything other than a Jab, if my fan was going to stop! I agree that the numbers look scary though in a J160, hence the reason for this post, to get some real life figures for the J160 and what others think of the numbers.

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I recently did my BFR in a Jabiru 160. All the speeds (Rotate, Approach Best Glide) are about 65 knots indicated & climb out at 70 knots. The high stalls I did had the ASI back to about 35-40 knots & landing I didn't look. I found it easy to fly but with me at 75kgs & a 110kg instructor the performance was shall we say leisurely at about 100 fpm and 70knots. The stall speed would have to be 45 knots or less in the landing configuration or it could not be registered with RA-Aus. 

Edited by kgwilson
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The 160 and 170 are not  much different to fly. the 170 is said to be harder to get down onto a short strip, it has alot of wing in reserve...

You might find the J160 more directionally stable - the wing to tail boom ratio is smaller. 

Both have similar stall characteristics. I think the 160 has a bit more flap area for the wing size.  

The 170 of course is rated for 600kg. It needs to bigger wing to do so.

 

Maybe get an instructor that can help you understand this stuff.  

In my opinion you shouldnt be deciding on a plane for the sake of a few knots of clean stall  on paper when the real world might be +/- 10 kts !

 

Help us understand exactly what you are scared of with the 55KCAS clean stall ? you should not be flying down at 55 kts without flap out in that aircraft  (IMO) . 

 

 

 

 

 

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I thought the HBird was pushing saftey without Flaps !

BUT 

Now I,ve seen the video of an aicraft without flaps OR ailerons.

It fies OK

spacesailor

Edited by spacesailor
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RFguy: Imagine you are established on finals / base to final turn at 65 KIAS, with approx 10 knots headwind. You forgot to put on the flaps because of turbulence / crosswind / distraction (pilot error / human factor) / stuck flaps due to mechanical fault. Suddenly the wind drops, or you encounter a wind shear and the IAS drops to 55 KIAS. The stall speed is 55 KCAS = 58 KIAS in J160. I am concerned it would be enough to stall the plane or drop a wing in a turn while you are too low to recover. It can also happen soon after take off. while you are 50 to 100 feet up in the air. Another possibility is being caught by turbulence / wind shear when making an emergency landing on top of trees in a forest in case of engine failure, and you forgot to put on the flaps for the fear of the inevitable!

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1 hour ago, kgwilson said:

The high stalls I did had the ASI back to about 35-40 knots

Does an ASI give an instantaneous reading, or is there a lag time due to the distance between the pitot inlet hole and the diaphragm, and then the response time of the guts of the ASI?

 

BASIC INSTRUMENTS FOR FLYING - ppt video online download

The ASI is an application of old mate, Bernoulli's 

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There is a time lag, but it is so small as to be of no consequence. What you are measuring is pressure, not airflow. The air in the tubing has to be pressurised, but the actual amount of air that flows in the system is miniscule.

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39 minutes ago, anjum_jabiru said:

RFguy: Imagine you are established on finals / base to final turn at 65 KIAS, with approx 10 knots headwind. You forgot to put on the flaps because of turbulence / crosswind / distraction (pilot error / human factor) / stuck flaps due to mechanical fault. Suddenly

If you are flying straight on base and your headwind disappears and you go into a marginal stall, the wing might drop a little. maybe- ( it is not a provoked energy stall in a steep climbing turn with no power- these airplanes are well behaved and subtle)

--- you will push the stick forward to regain airspeed, trade a bit of altitude and use  opposite rudder to pick it up the wing . Not much altitude lost.  And put on some more power.....Sorry, I don't see the problem.  

 

*shrugs shoulders*

and as for an EP landing and you forgot to use flaps  to get yoru airspeed down on final final ? that's your problem ! Of course, with electrical failure you might not have flaps.

 

Edited by RFguy
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6 minutes ago, Yenn said:

the actual amount of air that flows in the system is miniscule.

I agree that the amount of air (mass flow) is miniscule, but so is the degree of movement in the diaphragm as well as in the gearing and needle movement. Each movement takes time and those movements must reach equilibrium. That's where the lag comes from, isn't it?

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anyway, I think you will feel the stall, forget the airspeed meter.  your training will sense and snap your body into a stall recovery (or just jam on the power with a bit of nose down to accelerate the recovery a little) .It's not going to go down into a  instant spin from level like that unless you are in some sort of steep turn or terribly uncoordinated flying manouver. .....And if it happens on takeoff , after converting excess airpeed to altitude, you'll push the nose down and figure out what to do next...

Edited by RFguy
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