J170 - first impressions

[Chukcha]

HI all,

 

Our club has just swapped the J160 for a J170. I've just tried it out. having gone up with the instructor for the required type conversion, and than I did a couple of solo circuits.

 

Our club used to own a Jabiru LSA, in which I learned to fly. Then we switched to the J160. The new airplane seemed more docile, quite a bit more stable around the vertical axis, albeit it lost some climb performance, being heavier than the LSA with the same engine. The roomier cockpit and extra fuel were welcome changes. One thing I didn't like at all was the electrical flaps, but that, I suppose, is a matter of personal preference.

 

In the end, after getting used to the differences, I quite liked the J160. It was a very nice plane to take a passenger for a ride (provided the pessenger was not too heavy).

 

Now, my first impressions from the J170 were not very favourable. I didn't really notice much difference in the climb performance, but that could be due to many factors such as the amount of fuel, air temperature and humidity; to see the difference, the two aircraft would need to be tested by the same pilot at the same TOW side by side.

 

In the circuit, performance seemed more or less similar to the 160; the ailerons seemed a little heavier. Putting flaps down produced a pronounced nose-down attitude, especially evident on the final; this "nose dive" attitude could easily scare the dickens out of an unexperienced passenger.

 

I approached at 60 knots, flared and it floated ... and floated ... and floated. I've done about ten landings in it so far, and every time it would float, and it seemed forever before it touched the ground.

 

I have no doubt that the Jabiru people did a great job on this aircraft, and all the changes are well justified. Also, I'm not a very experienced pilot, and maybe I've had too little time in the J170 to learn to appreciate its advantages. This is just my first impressions, and in this thread I would love to read opinions of other pilots who switched over from J160 to J170, their impressions and comments.

 

Cheers,

 

Andrei

 

 

[Ross]

J170 vs J160

 

According to the POH, what is the Stall speed of each aircraft with full flaps deployed?

 

Regards

 

 

[Ultralights]

we have a new J170 also, and to stop the float on landing, aim for 60 over the fence, touch down at 55. no more float. remember it has a lot bigger wing and flap area than the 160. with full fuel and near MTOW, i aim for 65 over the fence and on the runway at between 55 and 60

 

 

[sseeker]

BlackRod,

 

I'd say the Va has something to do with the modified airframe (expanded wings + winglets maybe? Not sure...) most ultralights have a Va lower than there cruise. Like the J230 can apparently cruise at 120kts, yet its Va is 90... I think it's just in case something goes wrong. I know of one GA aircraft, the Diamond 40 infact that does the same thing, you *can* cruise is above Va and it's very capable of achieving it but it's Va is lower.

 

My response to the OP is pretty much covered in BlackRods post, the J170 is just another upgrade from the J160 which is an upgrade from the LSA all of which have the same powerplant.

 

 

[djpacro]

The RAA ground school notes on flight envelopes should explain why the J170 has a lower Va.

 

 

[sseeker]

You've got a good point there BlackRod, I think the J170 is an alternative to the J160 with bigger tanks etc... but in return you pay that price of lower usable load and lower climb performance?

 

-Andrew

 

 

[facthunter]

give and take

 

All aircraft are a compromise. The big ( 8 knots) variation in stall speed ( 20%) enables you to approach at a lower speed and otherwise you will float excessively as you have more excess speed to wash off. This means you can use shorter runways and there will be less wear and tear on the brakes etc. It also could be expecred to make the aircraft a little more sensitive to turbulence but probably perform better at gettimg airborne and climb on a hot day, with the same weight. Nev

 

 

[winsor68]

I think it is obvious that the maximum manoeuvring speed would be a little lower for essentially the same basic fuselage with a bigger wing... but both Va's are similar to or higher than the typical cruise speed of the J160/170- is this not a positive design feature. There are aircraft with a cruise speed higher than Va and even close to Vne. I find it comforting that the Jabiru is not one of them as this implies to me that it should have a good strong airframe...?

 

 

[Chukcha]

... aim for 60 over the fence, touch down at 55. no more float.

That's exactly what I was doing - 60 over the fence. After starting this thread, I was actually advised to try to approach at 55.

 

There are some that don't consider the J170 an "upgrade" on the J160.

As far as I understand, it is not exactly an "upgrade", it is a version aimed at better performance in hotter climates. Seems to be a compromise - gaining in some aspects, losing in others.

 

 

[Bruce Robbins]

Quote:

 

"My issue wasn't that the Va is lower than Vc or Vno - this I would expect. But it was how much lower it is for the J170 than for the J160. Sort of implies greater structural strength for the J160 than the J170?"

 

Hi BlackRod,

 

Va is not a function purely of airframe strength. It is a combination of structural strength and stall speed. The link provided in post #7 explains how it's calculated.

 

The J170 has essentially the same strength as a J160, but because the stall speed is lower, then the Va must be lower.

 

If you look at the specs for many of the European hotrods, you'll find high cruise speeds but low turbulence and manoeuvering speeds, because they have to meet a lower stall speed requirement.

 

A lot of GA aircraft actually quote different turbulence speeds based on how much weight you are carrying. The lighter you are, the slower you have to fly in turbulence.

 

Cheers,

 

Bruce

 

 

[winsor68]

Not sure I'm with you W68 . . .J160: Va 102 Vc 100

 

J170: Va 90 Vc 100

 

I think you would have to do a LOT of polishing to get 100 knots cruise from the J170 I fly... 90 seems a bit more realistic ( or do some people actually get 100knots clean from their Jabs?)

[Captain]

 

I do.

 

[Gibbo]

I would take a 160 anyday compared to a 170.

 

I have 260 hrs in a few 160's and at least 110 hours in a couple of 170's. Yes the 170 is better on short landings BUT I have found you really need to be careful in turns coming into final when the speed is starting to drop off. The longer wings also mean a reduced turn rate.

 

Longer wing also means that the aircraft *may* stall the wig tip a bit faster when completing a sharp turn. Very unresposive in high xwind landings.

 

Happy to make a 20kn xwind in a 160 (if pushed) but the 14kn limit on the 170 MEANS 14kn. For the record, my best xwind in a 160 was a certifable 26kn landing at Ceduna during a storm back in August and there is no way I would do that in a 170.

 

160 is a heap better in rough flying conditions...

 

Another rant is the Glass cockpit problems that every 170 suffers from.

 

Gibbo

 

 

[Bruce Robbins]

Hi W68,

 

The 100 knots is TAS, not indicated.

 

 

[Guest Pioneer200]

Hi, our club J160 does 100 knots indicated @ approx 2850 rpm ONE UP, probably closer to 95 when a bit heavier.

 

A bit off post but my 3 year old daughter Hayley went for her first flight with me yesterday, she loved it!!

 

 

[Guest Andys@coffs]

I'm sure that I read the need for the 170 was from flying schools who were circuit bashing in hot/high locations, where the 160 didnt get to circuit height 2 up at or near MTOW in a timeframe that the schools wanted. As such take the J230 wings and bash them on a 160. Net result, as Nev suggests, better climb but probably trading a few knots forward for those few fpm up... Different strokes for different folks and as I understand it the same compromises between the J200 and the J230. The 200, with its smaller wings can probably beat the 230 in straight cruise litre for litre and the 230 can outclimb the 200

 

Andy

 

 

[Guest Pioneer200]

Hi Black Rod, no booster seat, just a few cushions and the belt did up nice and firm

 

Next time I will use a seat or more cushions so she can see over the panel and forward and not just look out he side window.

 

 

[Tomo]

or do some people actually get 100knots clean from their Jabs?

Easily, out of the 120. At about 2850-2900rpm depending on the time of day, and temperature.

 

 

[Ultralights]

most i got from our schools 40 Hr old 170 was 95Kts at 2900rpm

 

 

[Chukcha]

Easily, out of the 120.

Same out of the LSA.

 

 

[kevinfrost]

We've had our 120 for nearly 2 years and at around 2925 true air speed is 107 kts, really pxxxxs my brother in law off in his 66 Cessna 172 especially @ 15 lts per hr.

 

He does have 2 extra seats though.

 

 

[winsor68]

For the $$$ those Jabiru 120's are certainly an appealing machine... I only have experience with the one J170. I guess for most school aircraft in training it sounds like 90-95 knots is more realistic as is typical of the school aircraft I fly. I have seen the airspeed increase a few knots from giving the leading edge a nice clean. Perhaps the 100knot cruise is something that private owners tweak from their 170's... or perhaps we will get it when we have polished our flying skills as students and hold the aircraft more balanced in cruise.

 

 

[Chukcha]

Thanks, David. I'll try it next time. I personally think that my instructor's recommendations of 60 knots approach speed come from the 'better safe than sorry' principal. We have very long runways at YGAW, and he would rather have me float a little than stall it on the approach :) .

 

Thanks everyone for your input, it was interesting to hear other pilot's opinions.

 

Andrei.

 

 

[Guest Pioneer200]

I used to approach in the J160 @ around 70 knots, but now having flown it lots find it much better approaching @ 65 knots.

 

If you approach @ 70 and don't cut the power until the flare you will definitly get 50m or so of float.

 

The 65 knot approach makes a huge difference, cut power when flaring and she settles down nicely.

 

Would not like to go to far below 65 knots on the approach though, the controls start to feel a bit clumsey and things feel a little unbalanced.

 

Have only ever flown one Jab (J160), would love to try the 230 and the 120, may have to do a flight up to the North Island one day and try these 2 @ Mt Maunganui, both were flown out from OZ for flight training at the Mount.

 

 

[sandman]

I was thinking of buying a J170 but it appears the 160 maybe a better aircraft for what I want, I'll keep my eye on this post. Cheers.