W&B and CoG Jabiru 170D/230D

[Roscoe]

BlueAd, that is good advice , They have done this before with many different students. I find the best teachers are ones that can adapt/vary a little to suit the student. I'm not at all concerned about the W&B for the training.... We are not going up there with a toolbox of housebricks..... BUT:

 

Actually the thing I wonder is : will I easily develop the intuition of 3 axis coordination, or will my brain / visual +hand eye acuity just not be up to scratch learning late in my life (49) rather than earlier. I guess I am dazzled by the learning rate of my 5 yo and 7.8 yo , and wonder if humans continued to be able to learn at that rate (at 5 years old) their whole life, what sort of place we'd live in.

 

Thanks for the Mackay offer ! I have a feeling the aircraft I buy where ever will be a long ferry home. Sort of reminds me of driving my first car I bought home some distance, barely held together learning to drive a manual gear shift for the first time doing it..-GLEN

Youre not too old!

My late father started his training at age 55 and despite struggling a bit with the theory, obtained his PPL and gave up Bowls due to his new found passion!

Made new friends and changed his life.

[RFguy]

Thanks for the encouragement. Yeah I am beginning a new chapter in life really. Particularly socially - a different bunch of people. Electronics hobby as a kid turned into work... Now work and hobby are too close, after so many years I need a change. The very unforgiving nature of flying together with the detail , and meeting new like minded people is the attraction. And flying to get around is handy- --what triggered this- flying around with my mate in his Cirrus regularly was enjoyable . which he is no longer doing as of last month. Its funny when he was practising IFR approaches I would have a mental sweat up absorbing and following everything (as if I was also performing the workload also) like a task overload due to not being familiar/practised -- glen

[facthunter]

People who fly RAAus and some GA these days are a mixed bunch compared with what was the situation in the 50's. Their "varied" backgrounds sometimes make issues complex. Good grasp of basic Newtonian physics is helpful. Sailing, gliding, motorcycle riding,tennis mountain bike riding good eyes for depth perception and keeping a lookout.. You will never know "everything" about flying . You can always learn more even in a limited sphere of operations. Fly within your limits and your planes limits and you will survive. YOU play the major part in how risky it has to be. ANY motor CAN FAIL at any time. Electric ones could easily become the best yet. Jets are by a wide margin at the present but they have NO soul or character.. Nev

[RFguy]

Electric is coming. 45kW cont /60kW peak motor is about 20kg including controller.

batteries need to improve by 10x. that is coming, also.

 

Needs battery storage. 1 hour of flying is 187kg of LFP.

 

Maybe wankel engine from 100LL driving generator, and have say 30 minutes of batteries at 50% power ? (93 kg)

 

I would have though a small JET mounted somewhere would have been the ideal backup. say 25% of ICE thrust (128kg max)

 

$USD4000 31kg thrust, about a litre a minute of JetA or kero. weighs 3kg.

 

http://www.kingtechturbines.com/products/index.php?main_page=product_info&products_id=55

[RFguy]

Jets are by a wide margin at the present but they have NO soul or character.. Nev

 

I don't think I want soul or character in an engine, I just want it to do its job !

[facthunter]

You will miss out on a lot then. Getting a plane to respond well and feel good in the controls and go where you want to put it , Face the challenge of starting a piston engine smoothly smoothly every time and other such skills rather than just press a button and hope the turbine doesn't drip out the back. Our planes are not to get you somewhere with an autopilot and all the mod cons . Going places? That's just an excuse we give ourselves. to indulge in all these experiences .. Nev

[RFguy]

You obviously feel deeper about the engine that I ! Maybe I will grow (back) into it. I probably felt the same in my own (auto) engine building days ...

[facthunter]

Simple Safe and affordable is the niche we operate in. SAAA build remarkable things including Jets one off. IF you have little feel for pistons you are definitely less safe and will do more damage than otherwise. It happens all the time. A jet engine gives no warning generally but they are about 10 times more reliable but well out of our price range. Probably small ones will not be as efficient and stink and make crook noises and suck in rocks on rough strips. You can't hand prop them either.. OK if I'm Going to London or somewhere but I've done as much of that as I care for. Nev

[RFguy]

Simple Safe and affordable is the niche we operate in. SAAA build remarkable things including Jets one off. IF you have little feel for pistons you are definitely less safe and will do more damage than otherwise. It happens all the time. A jet engine gives no warning generally but they are about 10 times more reliable but well out of our price range. Probably small ones will not be as efficient and stink and make crook noises and suck in rocks on rough strips. You can't hand prop them either.. OK if I'm Going to London or somewhere but I've done as much of that as I care for. Nev

suck in rocks, yes. indeed.

[Thruster88]

I don't think I want soul or character in an engine, I just want it to do its job !

With lycoming you get all three. ??

[RFguy]

anyway, I will meet Mr Rotax next week in the Brumby.

[Stuart Erskine]

Safety Thought.. How confident are you that you really do know the actual Empty Weight of your aircraft? Since important calculations and loading decisions originate from this critical weight, its vital to know what it actually is. Is the empty weight in the POH correct? Do you trust that the weight stated at time of CofA must be correct just because it couldn't possibly be wrong, given all the measures in place to prevent any such errors? If you are reading between the lines you may be in for a shock. Trust but Verify.

[facthunter]

TRUST only what you MUST. In the U/L field YOU can be THE Major player in the condition of your plane and how, where and when it operates. Nev

[RFguy]

"trust only what you must" is a good one.

Well I have read a few POHs now and are small errors and also many not fully qualified numbers that should not be blindly accepted.

 

So I am impressed with the Rotax. That Brumby goes off like a scalded cat on takeoff (compared to the Cirrus) .

I read through the Rotax English Operational manual this morning, there are a few little but important things missing from the Brumby manual, or that could be better.

I have not verified that aircraft (I am training in ) CoG and overall weight. Tough little aircraft though....

[Roscoe]

Safety Thought.. How confident are you that you really do know the actual Empty Weight of your aircraft? Since important calculations and loading decisions originate from this critical weight, its vital to know what it actually is. Is the empty weight in the POH correct? Do you trust that the weight stated at time of CofA must be correct just because it couldn't possibly be wrong, given all the measures in place to prevent any such errors? If you are reading between the lines you may be in for a shock. Trust but Verify.

Not quite sure of the point you are making.

So if i buy a brand new Factory built Aircraft with the stated Empty weight numbers in the POH, that I have to go and re weigh myself to confirm the Manufacturers numbers?

Can you clarify thanks

[facthunter]

The Basic Wt and index for any plane( Type) is pretty variable as mass and location of individual items, aren't always the same . Also it was permitted to alter thing s if the new figures could be established from the Original Condition OR last WEIGH and the calculated effect of the changes just carried out at the time it was done.. and appropriately documented and used. This process means that an error will/can be perpetuated till a reweigh is done. Reweigh means a "new" Basic Wt AND INDEX will be established together. You need both items to have the necessary information. to load your plane within specified limits. Weight and Balance. Balance ensures control is available normally. in the pitching plane.

Max wt based on PERFORMANCE criteria existing at the time ie. Density height , runway length, surface condition and slope and obstacles affecting the aircraft's take off path just determine a WEIGHT,(Mass) LIMIT and assume that the balance is taken care of in the normal LOAD sheet provisions. Rearward Cof G's (within the limit) will give better climb rates , cruise speed and ceiling results if you can do that. Nev

[Roscoe]

The Basic Wt and index for any plane( Type) is pretty variable as mass and location of individual items, aren't always the same . Also it was permitted to alter thing s if the new figures could be established from the Original Condition OR last WEIGH and the calculated effect of the changes just carried out at the time it was done.. and appropriately documented and used. This process means that an error will/can be perpetuated till a reweigh is done. Reweigh means a "new" Basic Wt AND INDEX will be established together. You need both items to have the necessary information. to load your plane within specified limits. Weight and Balance. Balance ensures control is available normally. in the pitching plane.

Max wt based on PERFORMANCE criteria existing at the time ie. Density height , runway length, surface condition and slope and obstacles affecting the aircraft's take off path just determine a WEIGHT,(Mass) LIMIT and assume that the balance is taken care of in the normal LOAD sheet provisions. Rearward Cof G's (within the limit) will give better climb rates , cruise speed and ceiling results if you can do that. Nev

All good and correct Nev. Just making a point to Stuart regarding perceived mistrust of the Manufacturers book figures.

[Roscoe]

All good and correct Nev. Just making a point to Stuart regarding perceived mistrust of the Manufacturers book figures.

And i appreciate the need for a re weigh if items are added/removed since original weigh

[facthunter]

Roscoe, done properly the "calculated" figures work fine for changes if you know what you are doing but I wouldn't see it as extreme if the CASA required a reweigh. One of a fleet of 5 similar planes on line by my employer was hard to flare. When it was eventually weighed fully it was miles out on the Index. Nose heavy. Just as well it wasn't as far out the OTHER way.

Generally there's room for skepticism with a lot of this. I'd trust Brumby to check from their records . BUT there's easy ways to do a rough check . IF you are close with the empty(basisc) wt the amount on the nosewheel (or the tailwheel) will be within a range. you can calculate. Have the pitch reference datum horizontal. (flying attitude) Please Note.This is not a substitute for doing the thing properly but may indicate a need for it. Nev

Edited August 31, 2020 by facthunter

[Old Koreelah]

And i appreciate the need for a re weigh if items are added/removed since original weigh

Good point, Roscoe. Everyone adds stuff, but you never hear of aeroplanes which have had weight removed.

[RFguy]

So... now that I can do W&B in my head in inches or mm or chains and grains

I've run some spreadsheets (and making more) on various aircraft. I can run many load scenarios and see 'what happens', and how tolerant various aircraft are to loading variations.

 

One thing owners of J230s in schools say they dont like them in school service so much because they can "run out of elevator" in a flare .

And the W&B calcs show that while the J230 CoG range is very broad, with medium fuel, and two POB, the airplane will be nose heavy - it is almost at the forward limit end of the range ..

Which might tell us why they are short on elevator.

Needs power to get elevator airflow at low speeds due to the amount of downforce required being nose heavy. (I think- I am not an aeronautical engineer but I do understand wings and math)

 

The calcs show that J230s with only pilots in the front seats need a bag of concrete in the back of the baggage area to bring the CoG at least back to the middle of the range.

Is this other's observation ?

[turboplanner]

So... now that I can do W&B in my head in inches or mm or chains and grains

I've run some spreadsheets (and making more) on various aircraft. I can run many load scenarios and see 'what happens', and how tolerant various aircraft are to loading variations.

 

One thing owners of J230s in schools say they dont like them in school service so much because they can "run out of elevator" in a flare .

And the W&B calcs show that while the J230 CoG range is very broad, with medium fuel, and two POB, the airplane will be nose heavy - it is almost at the forward limit end of the range ..

Which might tell us why they are short on elevator.

Needs power to get elevator airflow at low speeds due to the amount of downforce required being nose heavy. (I think- I am not an aeronautical engineer but I do understand wings and math)

 

The calcs show that J230s with only pilots in the front seats need a bag of concrete in the back of the baggage area to bring the CoG at least back to the middle of the range.

Is this other's observation ?

It's great to see someone being analytical and being able to get results. Looks like you may have found a J170 advantage ofver a J230 for some applications without spending a cent.

I've done about 8,000 to 10,000 truck analyses and the overriding lesson to that for me is "Never try to visualise the result" When you calculate the moments you know to whatever measurement standard you want even if that's tenths of a mm, and you can replicate that on the weighbridge.

[RFguy]

cheers Turbs. you said "Never try to visualise the result" . AMEN !. I AGREE STRENUOUSLY.

The results are surprising (needing that bag of concrete in the back of the J230) .

However J170C cannot have much bags at all - even with weight to spare- any bags with 2 x POB runs the CoG excessively aft....., which is why in the 170D they said they moved the engine forward (which results also in a bunch of changes at the tail)

With the J170D you actually can load the aircraft with the baggage and maintain aft CoG limit!

So, yeah J230- put a bag on concrete in the back,( AND WEIGH IT ALL TO CONFIRM -don't take my advice blindly) to confirm my suspicions .

J120 isnt so bad, because you cannot put much in it anyway before you go overweight- which you dont want to do much because at the specified MTOW 500kg the dirty stall is 45 kts- NO room to go overweight at all.

 

Turbs you wrote " Looks like you may have found a J170 advantage ofver a J230 for some applications without spending a cent. "- I think you meant the other way around, since a bag of concrete in the J170D will do you no advantage unless-- unless you want to carry concrete.

Edited September 21, 2020 by RFguy

[turboplanner]

Well there you go, I didn't listen to myself and would have screwed up big time!

[facthunter]

You can't argue with concrete evidence. Nev