Flap usage on Jabiru's

[Thx1137]

Thanks all for the replies, has been extremely informative. For those of you who feel like you are "falling" with full flap on, maybe you are leveling out before you get to ground effect, to high?

 

I noticed the same thing, but I now level out and use ground effect, it works stacks better, you get a lot lower though, and will make your passenger wonder!!

 

The reason I reckon it does it, is because when you level out, it slows down pretty quick, (with full flap) so if you aren't at the correct level, it will fall quickly, and you'll have to check it quick. But when you just have one stage of flap or none, it will give some lee way as to how high you level out, and just slow and sink a bit slower.

 

Just a thought?

I can relate to the "falling" thing however as long as your smooth and not too fast with bringing the stick back for the flare full flaps works great for me. If you give it a yank it or a bit early though I find it bleeds speed off pretty quick and the plane feels like a brick. That was one of the big issues I had when first learning to fly the Jab.

 

As for "flaps as required". Yes, but having a long runway does not "require" zero or one stage of flaps. It is an "option"! If the pilot wants to exercise the option and is comfortable with their ability to do so then who can complain!? We do have some flexibility as PIC!

 

The POH gives us a 'standard' way to do things which, of course, must be modified based on conditions. For me, given the conditions where full flap is "optional" I will still usually (unless I want to practice using less) use full flap because personally I never plan to use more runway than I need and I like standards/consistancy. :-)

 

Steven.

 

 

[flie43]

This is a great link on flap usage

 

http://www.aero-news.net/podcasts/casts/3/ann-special-feature-2008-05-12.mp3

 

Terry

 

 

[Relfy]

Dave,

 

I'd have to agree with you in that even though I find landing with full flap a little more challenging, I do it whenever I can, even in crosswinds, just to push myself and give my 'pilotage' a workout. I don't think flying is always about taking the easy way out. It's an evolving process and continual exercise of our skills.

 

Someone else posted a really relevant comment today asking the question 'when do others challenge themselves with training manouvres after gaining their cert'. I thought that was a really relevant point because I know myself that I feel I should be doing more e/f practice procedures to maintain my skill base rather than just flying over the countryside, thinking that I should be practicing more.

 

It's right about now that I feel Ian deserves a big pat on the back for all his work in building this forum, because discussions like this are what it's all about...pilots sharing skills and methodology. :thumb_up:

 

Great topic too Tomo. ;)

 

 

[sseeker]

Flaps as required, you don't *have* to use them. I've done flapless landings and they're not a problem, nothing to hard but I've always used flaps for glide approaches especially stage 1 because it generates the most amount of lift and gives you a nice nose down attitude. I generally apply the final stage of flaps when I'm sure I'm going to make it.

 

If you've read my other posts you'll see that the Jabiru POH isn't all that reliable, I think you'll find that most pilots that have flown Jabirus for a long time operate them on an experience side of things and don't really pay any attention to what's in the POH (which isn't the smartest thing to do).

 

Perfect example:

 

Fuel pump should be left on when starting the engine, most people leave it on for 5 seconds then switch it off (which is exactly what I do.)

 

But that's a little off topic, sorry about that.

 

 

[Tomo]

Keep it up guys/gals! Very good.

 

I'll join in when I find some time....

 

 

[Powerin]

Just picking up on the 5 knot speed difference Tomo mentioned in the first post, I was curious as to the difference that would make.

 

Working on (from the website) the J160 stall figures of Vso=48kts clean=53kts and landing roll=238m.....

 

Landing at 53kt instead of 48kt is 12% faster, but your aircraft has 22% more energy. Meaning you need 22% more stopping distance (52 metres extra), hit things 22% harder and theoretically do 22% more damage if you do. I'm not sure if that would mean 22% more tyre wear...but it probably would.

 

Can you tell I'm crook at home and bored?

 

Peter

 

 

[Powerin]

Hi Peter,So if you are 12% fast with 22% more energy, your stopping distance is not 22% more it is the square of the 12% speed or something like that because of the energy you carry at 12% faster speed, someone better at maths could explain it better, Rocketdriver is pretty good at that.

 

All I know is once on the ground, speed is your enemy, especially on a short grass strip, with no effective braking on grass and no reverse thrust.

 

David.

Hi David,

 

Yeah...as you said it's the square of the velocity. In this particular case I used 48kts and 53kts.....53 being 12% more than 48. 48 squared=2304 and 53sq=2809 which is 22% different. The percentages would be different for different speeds.

 

I used this calculator to double check the stopping distance and it is about 22%. You have to enter a friction coefficient between tyres and the surface into the calculator...the higher the number the better the stopping power. The site says an ideal coefficient for good car tyres on a dry surface is 0.8 but in reality it is more like 0.6 or 0.7.

 

To get a landing roll of 238m from 48kts for the J160 I had to use a friction coefficient of 0.13 ....pretty low! I wonder are other aircraft similar?

 

Have I driven you nuts yet?

 

Peter

 

 

[Powerin]

Good info mate, Thanks, but off course the friction thing goes to hell when you are landing on wet grass on a short strip right? In any case aircraft would be way worse than a car ... two tiny wheels braking ... a car has four with fat tyres.

Exactly right on all counts.

 

Peter

 

 

[Powerin]

Where is Henty?

Halfway between Wagga Wagga and Albury.

[Tomo]

Hey good stuff guys! Yes Powewin, 5kts mayen't sound much, but it hurts if you need to stop quick. And or if you like keeping your rubber for a bit longer...

 

Seeing as you got more time than me, you could work out the extra friction to the tyres at a 5kt difference. Just find the resistance factor, considering we use tarmac, and 100% grip at touch down or there abouts.

 

I better go, my lunch break has nearly gone, gotta get the Johny finished today.

 

 

[Powerin]

Hey good stuff guys! Yes Powewin, 5kts mayen't sound much, but it hurts if you need to stop quick. And or if you like keeping your rubber for a bit longer...Seeing as you got more time than me, you could work out the extra friction to the tyres at a 5kt difference. Just find the resistance factor, considering we use tarmac, and 100% grip at touch down or there abouts.

 

I better go, my lunch break has nearly gone, gotta get the Johny finished today.

Not sure how to work that out Tomo...I think once the full weight of the a/c is down on the tyres the friction would be the same. But I reckon there's a few factors in play with tyre wear.

 

Firstly (using 48 and 53kts as the example) when you hit the tarmac you have to spin up the tyre 5kts faster...which *should* also require 22% more energy in this case. As you touch down there would be a short transition period as the friction went from 0-100%. During this time the energy required to spin the tyre overcomes friction and it skids...which melts a thin layer of tyre. If you need more energy to spin up the tyre I would guess you would melt more off.

 

Secondly there's the extra tyre wear just from the extra landing roll. And don't forget your brake pads...they have to absorb that 22% extra energy. More wear there too.

 

Remember those percentages only apply to that set of speeds. If, say, you increase you speed by 5 from 5kts up to 10kts you are increasing your energy by 400%. Double the speed = 4 times the damage (as David says above).

 

Peter

 

PS...Ahhh those Johnny's...always in the shop :devil:

 

 

[flying dog]

Jabiru's and BREAKS!!?? :lol 8:

 

Sorry, did I miss something?

 

 

[motzartmerv]

Most POH's ive read say to effect maximum breaking for a short firled landing, that you should raise the flaps as early as practical after touchdown, to load up the mains and prevent skidding.

 

Even says it in the Jab flight manual.:ah_oh:

 

 

[Thx1137]

Yup. Gotta get the weight on those wheels!

 

Mind you,sometimes I think a bit of a headwind with full flaps would have offered more drag braking than the brakes on our aircraft!

 

 

[Tomo]

Did a few experimental landings this morning in the 120.

 

Full flap - normal landing configuration.

 

And a 1st stage flap landing.

 

Both at 65kts initial approach speed, normal hold off and landing on both, just over stall speed.

 

Full flap was ideal, flared and it slows down reasonably quick, for a bit more of an abrupt landing, ie, runs out of lift faster.

 

1st flap was nice for touch down, but she floated and floated and floated..... took forever to slow down, was a nice landing though. But I can imagine a learner having trouble trying not to balloon it - ie pull back a bit much and climb. Not to mention a strong crosswind. I only had about 4kts this morning.

 

I actually video'd it all, so you can see for yourself. I'm not sure if I can get it edited and uploaded before I leave tomorrow, but I'll try.

 

 

[poteroo]

If you need heavy braking for a short-field landing in a Jabby then you're trying to fit into where you probably shouldn't be going. Aerodynamic braking is cheapest and safer. Allowing the nose onto the ground immediately you touch, then braking heavily - seems to be a primary reason Jabby's depart the strip left.

 

happy days,

 

 

[poteroo]

CFIcare,

 

We could argue the pro's & cons of short field techniques for hours, but I'm sure you know what I meant by that. In the Jabbys case, it isn't the greatest braking system because it can't be used differentially in order to help in direction and also to create moredrag via the wheels.

 

It's been my experience that where you need a short field technique, it's often coupled to needing a soft field, or a slippery field technique too. In either case, heavy braking is risky. I guess you then need to define maximum braking as the most you can use on any given surface.

 

happy days,

 

 

[poteroo]

You're absolutely correct. I'm just regurgitating theory.

 

happy days,

 

 

[Tomo]

A couple of circuits in the Jabiru 120 at Dalby before heading to our farm strip. First one was full flap (landing configuration) and second was 1st flap, note glide difference between them both on finals. About a 5 kt crosswind from from the left. Also first one was a slightly powered approach, whereas second was a complete glide. Illustrating the difference between full and only one stage of flap when turning final at similar distance. Also approach angle. I still basically touched down almost where I wanted to on both, 3rd line was the aiming point.

 

 

 

[Tomo]

No same approach speed on both, same height turning final at the same distance on both. You can see from that, that full flap puts you on a much quicker descent, as per the extra power needed.

 

Had 60ltrs of fuel and myself making a take off weight of about 385kg.

 

Approach at 65kts - as per POH, (to fast for that weight in my opinion, but I did it just to demonstrate)

 

I may have held off a bit longer on the first one - it was my first landing for about a month, so was still warming up to it, basically stalled it on. And as you can see, Jab's will float depending on weight and speeds, you could see how students have trouble at first of not ballooning it hey? Patience is the key to success!

 

 

[facthunter]

Considerations with flap usage.

 

A clean aircraft like a Jabiru will tend to float a long way without flaps (especially if you are a bit fast and/or the idle speed is a bit high).

 

Flaps give you the opportunity to reduce your approach speed, and get a better view over the nose. You can also achieve a STEEPER approach, if you don't use much power.

 

The final stage of flap gives extra drag as well as a bit of extra lift. This will give you potentially the steepest approach, and the shortest hold-off. If you get low on the approach you will not have as much power to spare to restore your approach path, due to the extra drag. Gusty conditions would be better handled with less flap especially if the wind has a significant headwind component.

 

The go around with full flap can be challenging in some aircraft especially if the trim is adjusted for the slower approach speed. Firmly applied forward stick is needed till the aircraft is retrimmed, and the aircraft will not perform too well till it is cleaned up. This can get a little untidy if not practised till proficient. There is some argument as to when the flap should be retracted from FULLY down, with some aircraft, as when heavily loaded or hot conditions, there may only be marginal climb performance available in that configuration. Nev

 

 

[Tomo]

Nice landings Tomo, nice flare and a nice clean hold off, you only knew you had touched down from the noise of the wheels n the black stuff.What does the POH say the Vso is on the J120 at Max weight, is it 48 as in the J160? If the POH says 65 knts approach you could assume around 50 Knots based on approach at 1.3 x Vso. If so 50 knots seems high, isn't it supposed to 45 max for the category and if so the approach should be around 60 not 65, but I don't know much about Jabs. Looking at the length of the hold off 65 was certainly fast for the weight, but still a good landing son.

 

David

Thanks David :thumb_up:

 

This is an exert out of the POH -

 

1.4 J120-C PERFORMANCE AND SPECIFICATION SUMMARY

 

 

 

 

• Gross Weight 500kg (11102 lb)
   
   
   
  
  
   
   
   
  
• Top Speed at Sea Level 120 KCAS
   
   
   
  
  
   
   
   
  
• Full Fuel Range1 380 nm at 75% power
   
   
   
  
  
   
   
   
  
• 450 nm at most efficient power setting
   
   
   
  
  
   
   
   
  
• Rate of Climb at Sea Level2 500 fpm
   
   
   
  
  
   
   
   
  
• Take-Off Distance 400 m
   
   
   
  
  
   
   
   
  
• Landing Distance 300 m
   
   
   
  
  
   
   
   
  
• Stall Speed Clean 49 KCAS
   
   
   
  
  
   
   
   
  
• Stall Speed Flaps Full Down 45 KCAS
   
   
   
  
  
   
   
   
  
• Fuel Capacity 64 L Useable
   
   
   
  
  
   
   
   
  
• Approved Fuels AVGAS or MOGAS with RON of 95 or higher.
   
   
   
  
  
   
   
   
  
• Maximum Engine Power 85 hp @ 3300 RPM.
   
   
   
  
  
   
   
   
  

 

 

 

 

 

 

[Tomo]

David, was it just my uneducated impression or did Tomo have a flatter approach than would be possible coming in over the trees at YWVA?

You may have a steeper approach, though if you look at the altimeter It'd still clear a reasonable obstacle. Though I made that first circuit to match the 1stage flap one, usually I am a little closer and a full glide on that to. But just for illustration I did that.

 

Tomo - that second landing was sweeeet indeed.

A few questions on the technology, if you wouldn't mind:

 

Camera type?

 

Camera Mount?

 

Sound recording via?

 

Editing software?

Thanks Don, I try my best! :big_grin: (you need to do good, cause you have all the people in the hangers watching! and they usually know who's driving! )

 

Ok, don't mind at all:

 

- The camera mount is this gizmo I made up after work one day -

 

[ATTACH]10486.vB[/ATTACH]

 

It attaches on the drop down ledge behind your head on the roof, works great actually. Not sure how it'd go with a passenger but in a 160 it might be more room and you could fit it between your heads. (better view that way :big_grin: )

 

- Camera type is just a Sony camcorder (8mm digital vhs type - old I know but works still). - But I made the mount to fit anything, as you can see one of my still digital camera's on it when attached to the dresser cabinet. You just screw the screw up on the bottom into the camera.

 

- Sound recording was just camera speaker, but I can record intercom by hooking up a line recorder on the passenger headphone output jack (just use an adapter).

 

- Editing software is iMovie on the iMac computer, my iBook G4 is just to slow, so I have to use Dad's iMac.

 

Next time I want to mount it in such a way so you can see the ASI and a few more instruments. That way you can see exactly what is happening.

 

Congrats on your Pilot cert!

 

 

 

[bilby54]

Its up to the pilot to operate the AC safely for the airfield he is operating and within his capabilities. Not follow POH blindly. As the HFactors exam taught us...... analyse and manage the risks .

Hi Jet,

 

The statement; "not following the POH blindly" bothers me and ask what you mean there?

 

Most landing accidents are caused by pilots not following what is in the POH. There was a percieved problem with the J160 needing a big bunch of runway to land but if you read the book and apply what is in it, the problem does not exist.

 

 

[jetjr]

What bothered you?

 

You are the pilot, you are flying, you make the call on flap use for the conditions and runway availiable.

 

There are too many variables to just follow POH without thinking about it. If it were written to suit every loading and condition it could be huge.

 

Now if you are saying " how should I use the flap in an aircraft I dont know well or flown before" then the POH is the right place to begin.

 

After say 500 landings I expect youve worked out which method works best for you and the aircraft in the situation youre in