How much does the C of G move aft with fuel burn, in a Bonanza

[Ratshit]

In another thread (Any C210 at YSBK), the following statement was made:

Originally Posted by Zhaadum

We were at max takeoff weight and I had to arrange it so as C of G moved aft when fuel burned off we ware ALWAYS in limits until landing.

This got me thinking!

Bonanza's (particulaly the V-tails) have always been a bit more sensitive to C of G issues than many of their contemporaries, but is there really a danger of the C of G moving outside the aft limit with fuel burn?

That is what I have always been led to believe, but having bought a Weight and Balance program that is custom made for the Fork-tailed Dr Killer, that clearly is not the case. Yes the C of G does move slightly aft with fuel burn, but the envelope also "moves aft". The end result is that if the V35B is within its C of G limits at TO, it will be within limits after 1, 2, 3 or 4 hours in the air.

With my V35B, it would seem that provided you are at or below max weight and within the C of G envelope at TO, and you land with 45 min fuel in the tanks, then it will stay within the envelope throughout the fuel burn.

Anyone care to comment for the A36?

R

[Chimbu chuckles]

The aft limit is linear in the A36, 2227mm aft of the datum.

It would be possible to do if loaded rediculously aft to begin with...if the seating was arranged by a moron and you then ran the tanks dry...it would basically have to be almost a deliberate act.

How much the CofG actually moves as fuel burns off in a Bo is situation specific...if you have an aft CofG at ZFW it will move a lot further as fuel burns than if you are in the middle of the envelope at ZFW.

[Ratshit]

Originally Posted by Chimbu chuckles

How much the CofG actually moves as fuel burns off in a Bo is situation specific...if you an aft CofG at ZFW it will move a lot further as fuel burns than if you were in the middle of the envelope at ZFW.

CC - you are correct but the movement is not as great as some would have you believe, and even for the V35B, if you start not above max TO weight and within the C of G envelope, it seems to me that you will stay within the envelope as long as you don't run the tanks dry.

I have always thought that you could start within the envelope and fly yourself into an "out of C of G" situation.

R

[john_tullamarine]

Not type specific but useful things to keep in mind .. not much different to running ballast calculations at the end of the day ..

(a) if the actual loaded CG is forward of the tank arm, then fuel burn moves the CG further forward

(b) if .. aft .. burn moves it further aft

.. so the effect is very dependent on the loaded CG .. if the fuel arm is within the envelope limits (ie the aircraft can be loaded either forward or aft of the fuel arm, burn can move the CG forward or aft according to circumstances.

(c) be VERY wary of aircraft with non-prismatic tanks .. ie the fuel load arm varies with the quantity of fuel. This can be a real trap if the usually quoted full tank arm is used without thought ... I've seen many a chap (including some weight control folk) get caught out with this ...

[bushy]

C of G

Data and method for calculating G of G is in the flight manual. That's what it's for. The fuel tanks are very close to the G of G and so will not move the G of G very much as the fuel burns off.If you enter the details from the flight manual into a good flight planner that makes it much easier, and it will calculate the C of G for both takeoff and landing.
You may also find that bonanza's, and barons will both bang their tails on the ground during the loading process, if you let them. This will happen if they are correctly loaded, but I always loaded back seat pax first, so I could make sure the doors were properly closed. Then, with no weight in the front seats a pax stands on the rear step, which is alongside the rear seats, the balance is all wrong. At this point, the nose often lifts and the tail hits the ground. Most embarrassing. But once you are all aboard the loading is correct, because no-one is standing on the step.
You soon learn ways to prevent this.

[Chimbu chuckles]

Like I said, with a Bonanza, you can do it but you'd have to be a bit thick.

5 or 6 years ago I designed a load system for my Bo in excell...it's very clever...all I need do is type in pax weight in the seat row they will occupy and I get a ZFW CofG. Type in the number of liters at engine start and they are converted to KGs and a TOW/CofG is calculated instantly. Type in the burn and you get a Kgs in the tank on landing and and landing CofG. I scanned the original DCA POH CofG envelope and incorporated that in the spreadsheet too so it is a simple matter to print it off and plot the three positions in seconds...or just look down and eyeball them.

Example

Row 1 90kgs of pilot and pilot stuff.
Row 2 180 kgs of pax and pax stuff
row 3 130 kgs of pax and pax stuff or frieght.

ZFW/CofG 1433/2243. That is 200kg below Mtow and 16mm behind the aft limit.

200liters/144kg of fuel.

TOW/CofG 1557/2212. 56kg under Mtow and 15mm inside the aft limit.

Enroute the CofG will be exactly at the aft limit, 2227mm, when you have burned 100 liters of fuel. If you land with 60 liters on board you will be at 2233mm and if you land with fixed reserves only 2236mm...9mm outside the aft CofG limit....doesn't sound like much but you are definately in experimental test pilot territory. The CofG has moved 24mm from takeoff to landing with fixed reserves intact.

You could add 77 liters of fuel and that would bring you up to MTOW, 1633kg and a CofG at takeoff/landing of 2201/2224 so 3mm inside the limits...might even be worth doing if the fuel where you're going is really expensive relative to where you're leaving. The CofG has still moved 23mm.

If you move 1 pax from the 3rd row to sit next to you instead you get TOW /CofG 1557/2138 and a CofG on landing with fixed reserves of 2156mm...71mm inside the aft limit. The CofG has travelled 18mm during the trip.

[Ratshit]

Maybe I am just getting old, but the Wt and Balance Charts for the V35B are among the most complex I have seen.

I bought a program called eFlite (see www.eFlite.com), that is customised for my aeroplane. Very easy to use and provides a graphical representation of the Wt and Balance - plotting the TO, Landing and Zero Fuel situation within the CG Envelope. Makes it easy to ponder statements such as the one in the first post..

R

[runway16]

A simple statement :

Yes, with the Beech 35/36 series you can end up with a CG beyond the aft limit (usually after fuel burn off).
It can get interesting to have to push the stick forward at round out instead of it coming back.

History would record that the Beech 35/36 series are no worse than any other brand of aircraft that has an increasing aft CG with fuel burn off. It just means that you have to fly the aircraft within the known limits of the machine and that includes the W&B.

Know your machine and fly safely gentlemen.

[Ratshit]

Originally Posted by runway16

A simple statement : Yes, with the Beech 35/36 series you can end up with a CG beyond the aft limit (usually after fuel burn off). It can get interesting to have to push the stick forward at round out instead of it coming back. History would record that the Beech 35/36 series are no worse than any other brand of aircraft that has an increasing aft CG with fuel burn off. It just means that you have to fly the aircraft within the known limits of the machine and that includes the W&B.
Know your machine and fly safely gentlemen.

"Yes, with the Beech 35/36 series you can end up with a CG beyond the aft limit (usually after fuel burn off)"

Runway 16 - the intent of this thread was to challenge that statement, at least in relation to the BE35!

"Know your machine and fly safely gentlemen"

Yes, indeed! And having flown nothing much other than the V35B for the last couple of years, I probably know it better than anything I have flown in the previous 35 years.

So what have I learnt?

1) Its much easier to load it out of the rear C of G than I had previously thought.

2) If you load it so that it is at or below its Max TO weight, and within its C of G envelope, it will stay within the envelope unless you fly it down to only fumes in the tanks. I never fly it with less than +15% and 45 min reserves, so this is not an issue for me. The C of G will sit on the aft limit only.

I am tossing around upgrading to a BE36, so this is of interest to me. If you believe CC (and I do cause he seems to be a font of much aviation wisdom), the BE36 is much the same.

R

[Chimbu chuckles]

The BE36 is not as sensitive as the V35 because when they designed it they moved the wing back a bit...but put enough stuff in the back of any aeroplane and you'll go out the back...I remember landing C185s with the CofG so far aft that if you used flaps 40 the control column hit the forward stop and stayed there until you went back to flaps 30. Three point landings became one point landings as the tailwheel gently arrived first ...with the BE36 you can carry LOTS and if loaded with a modicum of thought you'll stay well within the limits.

4x100kg adults+40kg bags and 250 liters of fuel will have you taxiing at MTOW and the CofG between 2100 and 2122, over 100mm inside the aft limit throughout. 210s may carry more but not with as much elan

[Ratshit]

CC - Don't tell my mates, most of whom are confirmed Cessna drivers, but the Fork-tailed Dr Killer has converted to Beech.

I thought a newish C206 was the machine for me (cause I think the newest C210 in Oz is now near 20 years old) but the 206 is just too slow.

I quite like Mooneys (particularly the ones with IO550s) but they are not ideal for some of the places I need to go (sit a bit low to the ground).

I just can't get excited about plastics (although a Columbia seems to have gained my brother's affection).

I mostly use the V35B for personal transportation but there are times when I need to carry more - over a long distance.

The Pipers will haul the load but are too slow.

The Missus didn't win the $30M Xmas Gold Lotto so I had to shelve my plans to go to France to collect a TBM850.

Which leaves me with a Bo.

R

[Chimbu chuckles]

An E55 Baron would carry the extra load for you...at a significant DOCs premium...but an A36 would have the extra capability you require occasionally with identical DOCs as the V35.

Agree...TBM700 or 850 is the dog's bollox as long as cost is not the determinate factor.

[Schmacko]

Why would anyone want to fly a bonanza anyway ?

[Ratshit]

Originally Posted by Chimbu chuckles

An E55 Baron would carry the extra load for you...at a significant DOCs premium...but an A36 would have the extra capability you require occasionally with identical DOCs as the V35. Agree...TBM700 or 850 is the dog's bollox as long as cost is not the determinate factor.

CC - Yes, and E55 or 58 Baron would work but hard (though not necessarily impossible) to justify turning the second donk for personal transportation. There is the old single vs twin argument. Personally I try to avoid flying at night in a single, but then I don't give a second thought to flying solid daytime IFR in the same aeroplane - go figure! I guess psychologically I convince myself that in the event of an engine failure I will pop out the bottom with enough room to find somewhere to park. Certain these days with terrain displays on GPS moving maps you can dodge a few hills on the way down through cloud.

R

[john_tullamarine]

Maybe I am just getting old, but the Wt and Balance Charts for the V35B are among the most complex I have seen..

I wouldn't have thought so ... in general the most complicated are trimsheets for those aircraft which are trimmed at ZFW and then one needs the loaded CG for trim settings.

Suggest that you have a look at birds such as the GII .. there are a few such trimsheets around ... one ends up with two envelopes superimposed with a fudge grid to make it all work.

At the end of the day, all the light aircraft have fairly straightforward trimsheets .... and, if designed sensibly, they all look pretty much the same in principle and use ..

[Ratshit]

Originally Posted by john_tullamarine

Maybe I am just getting old, but the Wt and Balance Charts for the V35B are among the most complex I have seen..

I wouldn't have thought so ... in general the most complicated are trimsheets for those aircraft which are trimmed at ZFW and then one needs the loaded CG for trim settings.

Suggest that you have a look at birds such as the GII .. there are a few such trimsheets around ... one ends up with two envelopes superimposed with a fudge grid to make it all work.

At the end of the day, all the light aircraft have fairly straightforward trimsheets .... and, if designed sensibly, they all look pretty much the same in principle and use ..

"Suggest that you have a look at birds such as the GII"

GII (?) - give me a break man! The biggest thing I have any time on is a C402.

R

[john_tullamarine]

... sorry, buddy ... but that's the way things are ... just keep it in the envelope and life is cool ...

[bushy]

Interesting

There are some interesting things here. I believe we have had sucessful forced landings in Australia at night. Surprising.
I remember reading american figures which showed that you are more likely to be killed in a twin engined aircraft than a single. Fatalities from engine failures were less, but prangs from other causes more than made up for it. Singles are simpler, and it appears, safer because of that.
Australia has a history of scud running and cfit in IFR equipped aircraft. Many of these are avoidable if the pilot is IFR qualified. We seem to make IFR training and flying so hard that hardly any of our pilots do it, and there are too many avoidable cfits
Peole talk about the KISS principle. We seem to do the opposite. And it costs.

[Chimbu chuckles]

so what's a little thread drift between mates

It's a worthy direction.

RS do you have an electrically powered back up AI?

If not your workload will be high gliding down on partial panel.

Don't get me wrong I do fly my aircraft at night and a little 'soft' IFR but only rarely...I avoid it if I.

Why?

I really think it is more a 'getting old/running out of lives thing' myself. I used up 7 of em in PNG...at least.

The basic facts are that no statistics can say with absolute certainty that singles are less safe than twins or visa versa.

In my view a well trained, skillfull and current pilot in a moderately loaded Baron can fly away from an engine failure every time...loaded to average 'private use' weights they'll happily climb on one engine at 500'/min...bloody sight better than a single after an engine failure.

Well trained and skillfull being the big problem....in my view virtually no private owners would spend the time and effort required to maintain the levels of skill required...a good two hour workout with a knowledgeable instructor every 6 mths and a few hundred hours between.

I think given the realistic amount of time I have spent in IMC in my Bo over the years...it would struggle to be a few hours total...maybe 1-2% of my total Bo time I cannot justify a second engine, vac pump, generator etc.

If I was doing lots of IFR/night flying I would definately get a second electric AI and fit a back up generator as those are failures you're likely to have to cope with...engine failures are incredibly rare overall, even with the abuse many engines suffer under...a well maintained engine that only you fly regularly and with a good all cylinder monitor I think is incredibly reliable. Take out the fuel starvation events from the forced landing stats and pure mechanical failures are rare indeed...statistically almost irrelevant.

That said if I as doing lots of over water flying I would want an E55 Baron...or if I ever get to a point, and it's not likely, where the extra cost of a twin is not a factor...they are the sexiest civil piston aeroplane ever built. ...but really short of living on King Island and flying a lot I cannot see a Baron increasing the safety aspects of my private flying anything like enough to justify the recurrent training and 2xDOCs...after 12000+ ME hrs I have long since lost the thrill of a handfull of throttles.

[Brian Abraham]

Have an Excel sheet made up for weight and balance which can be easily adapted to any GA type. Sample graphic below allows instant assessment of fuel burn influence (blue line in this case).

Anyone wanting a free copy (no steak knives included) let me have relevent details and I will adapt.