Weight & Balance effect pf Landing gear retraction
 

When studying the Arrow IV weight and balance in the handbook - I notice that it includes a moment figure for retraction of landing gear - it implies that you add this to find your total moment from which CG position is calculated.

My question is:

Shouldn't 2 results be considered to ensure that CG position remains within the envelope under both conditions ie during retracting and when stationary, either up or down. No mention either of LOWERING landing gear, presumably as this is under gravity and the torque just isn't there to affect moment?


Can anyone explain why 2 figures are not calculated? If it is becasue the effect is nominal then why bother mentioning it at all? After all the CG could be critical at either side of the envelope.

I don't have the numbers to hand, but I recall that when I last looked at the W&B for an Arrow 3 it is possible to be over the top with 4 adults and a bit of baggage, but be in balance on the wheel up calculation, and out on the wheels in transit numbers. Personally, I do both calcs to make sure it is on the graph for both sets of numbers.

It will fly over weight and out of balance, but it sure as hell makes an insurance claim into non claim should it arise, which, if you are far enough out, it will.

Do the maths, fly by number and live.

I thought that doing 2 calcs would be wise - thanks for confirming.

The worked example is poor in the handbook - it should make it more clear that 2 conditions are important. I will add the effect of retraction to be sure.

It is only a moment of about 819 which at max weight 2700 shifts the CG by a third of an inch and at lower weights this increases to 0.4 inches. So if you are near the edge of the envelope retraction is a factor, and at critical stage of course.

I don't know the Arrow 4, but the Arrow 3 I fly has a moment figure to add for "gear up", presumably to do with the C of G of the undercarriage shifting when you raise it.

It's dead easy to calculate both numbers and plot both dots. If they are both inside the box, all is well. If one or both is/are outside, ...

Corvus

Bear with what may sound a daft question.

Is it by any chance a 'winterized' Arrow where a larger battery is fitted in the engine bay instead of behind the passenger compartment?

BTW, I agree with Keef that it's easy to calculate both numbers.

Not sure about the battery location in the aircraft that I will be flying - In fact I am really just preparing in my armchair prior to some training, and it just ocurred to me that the handbook does not make it clear that 2 calculations would be wise. I am now convinced and can see a simple way to consider both.

My guess is that the Arrow I will fly will not be winterised as it is in Florida!

Corvus

I wouldn't assume anything frankly, I've come across a winterized version in a temperate climate where it had been bought second hand.

The reason that I asked is the combination of moving the battery from the rear to the front and also using a big heavy unit does have a significant effect on w&b compared to the basic aircraft.

Enjoy yourself :O

Yes, I've flown Warriors with the battery 'up front' and 'behind'
and it does make a considerable difference to the CofG,
the important thing is to use the specific W&B chart for that particular aeroplane, not a general one.