Weight & Balance and Landing Speed - Piper Comanche

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TonyW
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Joined: 03 Jan 2016, 17:22

Weight & Balance and Landing Speed - Piper Comanche

Post by TonyW »

Hello,

Some of this is going to sound very geeky, but I'm trying to get "as real as it gets"!

Following from another of my posts asking about ballooning in the landing, from the replies I got it seems that I've been approaching too fast. So I decided to do a chart of a range of weights I would normally fly. Based on just the pilot (based on my own weight of 60Kg - quite light), no baggage and only 20% fuel up to a full aircraft of four people, all with baggage, at 80% fuel, I came up with 32 scenarios with the following being heaviest and lightest payloads:
Lightest Payload is around 900Kg = 2,000 Lbs approx.
Heaviest Payload is around 1,300Kg = 2,870 Lbs approx.

Would 2,870 Lbs be considered a heavy payload for this aircraft?

Is this information actually useful for anything? How do I calculate my landing speed for the different weights? I've also looked at pages 71 & 72 of the Manual regarding weight and balance loading forms but although I understand the centre of gravity concept and how it would affect the balance of the aircraft I have no idea how to calculate Datum or Moment or whether I need to actually do anything in the aircraft to ensure that the c/g is correct?

Any advice would be appreciated.

Regards,

Tony

speedy70
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Re: Weight & Balance and Landing Speed - Piper Comanche

Post by speedy70 »

Tony the best thing you can do,is practice and more practice.

Find a very long runway like Honolulu and approach fairly low and then slow down until you are just above the runway and as the aircraft sinks try to keep flying by gently pulling the nose up until the aircraft ceases to fly.You have landed!!!!!
It is very good practice if you can get the stall horn to just sound as you touch down.
Just keep trying,look through the windscreen and not at the instruments.

Let us know how you get on.Never mind about weights just use you and a passenger.

Cheers Chris

TonyW
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Joined: 03 Jan 2016, 17:22

Re: Weight & Balance and Landing Speed - Piper Comanche

Post by TonyW »

Hi Chris,

Thanks for the reply. I will just keep practising as you suggest. As I have VFR Photography Scenery for Ireland (and some for UK also) that's where I usually fly. Both Dublin and Shannon have quite long runways so I'll practice on these a bit more before landing in the regional airports. The wider runways also help because with the ballooning I can drift off centre line when I lose sight of the runway.

Regards,

Tony

speedy70
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Re: Weight & Balance and Landing Speed - Piper Comanche

Post by speedy70 »

Hi Tony,
Don,t baloon reduce speed.
I will do a landing in the comanche tomorrow and try and make notes of the speed at various points.

Fly slowly on approach and reduce speed by pulling the throttle back not pulling up on the yoke.

Cheers Chris

speedy70
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Location: Devon,UK

Re: Weight & Balance and Landing Speed - Piper Comanche

Post by speedy70 »

Hi Tony.

This is the cherokee but the system is the same.Study it closely and then have a go at applying it.

https://www.youtube.com/watch?v=8uXzh2eJU1k

Cheers chris

Alfredson007
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Re: Weight & Balance and Landing Speed - Piper Comanche

Post by Alfredson007 »

TonyW wrote: Is this information actually useful for anything? How do I calculate my landing speed for the different weights? I've also looked at pages 71 & 72 of the Manual regarding weight and balance loading forms but although I understand the centre of gravity concept and how it would affect the balance of the aircraft I have no idea how to calculate Datum or Moment or whether I need to actually do anything in the aircraft to ensure that the c/g is correct?
Tony
It is useful, to a point, to approximately know the optimum approach speed, so you are safe from stalling either in final or too early during the flare and that you do not balloon for too long due to high speed. There are simple methdos to calculate the stall speed for yourself, or you can use precalculated charts or you can try it in the air, stall the aircraft in landing config and multiplie the stallspeed by 1.3x Ie. 60mph stall x1.3 = 78mph. Problem here is that you should use CAS rather than IAS, because IAS may have different error in different speeds. For example, Cessna 172R stalls at 33KIAS, but 40KCAS, so the airspeed indicator shows 7 knots wrong, but at higher speeds the error is smaller. Most GA planes though have less error.

As for CoG, some airplane manuals tell you the easy way to calculate it by yourself, or you can google for excel sheet or another internet calculator for your plane (IRL it must be the exact plane you are flying, because individual planes have different equipments etc).

TBH, i've never calculated CoG for Comanche because i think my loads are always safe. Of course this would be dangerous IRL. I know that in C172R/S you really need to do crazy loadings to get out of the CoG envelope, ie. have a light pilot and 2 fat fellas on backseats etc.

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AKar
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Re: Weight & Balance and Landing Speed - Piper Comanche

Post by AKar »

TonyW wrote:Is this information actually useful for anything? How do I calculate my landing speed for the different weights?
The stall speed is proportional to the square root of weight in 1 g flight (or that of lift in any kind of flight). Utilizing that info, it is easy to calculate the stall speeds (and the approach speeds as well, if they are simply stall speeds multiplied by a factor) to convenient weights, if the handbook value is for the maximum weight.

Take the Comanche as an example; it quotes an approach speed of 1.3 times the stall speed. Let us assume a stall speed of 64 mph at full load (3000 lbs), and full flaps. The approach reference speeds would be extremely easy to estimate with Excel for instance, by simply using a formula =SQRT([YOUR CURRENT WEIGHT]/3000)*64*1,3.

The results would be:

3000 lbs 83 mph
2800 lbs 80 mph
2600 lbs 77 mph
2400 lbs 74 mph
2200 lbs 71 mph
2000 lbs 68 mph.

It makes a one starting point.

-Esa

TonyW
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Joined: 03 Jan 2016, 17:22

Re: Weight & Balance and Landing Speed - Piper Comanche

Post by TonyW »

Hi Chris,

I've just looked at this video and found it very informative. The more I think about this the more I realise that speed is my issue, as well as the feeling that I'm too low just before the threshold.

Anyway - what I've learned is - practice, practice and more practice!!!!!

Regards,

Tony

TonyW
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Posts: 70
Joined: 03 Jan 2016, 17:22

Re: Weight & Balance and Landing Speed - Piper Comanche

Post by TonyW »

Thanks Alfredson & AKar,

Maybe I'm being a bit pedantic over weights and speed, but I'll use the info you've given me and will add in the suggested formula to my various weight scenarios I already described which is on a spreadsheet.

Regards,

Tony

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mallcott
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Re: Weight & Balance and Landing Speed - Piper Comanche

Post by mallcott »

TonyW wrote:Thanks Alfredson & AKar,

Maybe I'm being a bit pedantic over weights and speed, but I'll use the info you've given me and will add in the suggested formula to my various weight scenarios I already described which is on a spreadsheet.

Regards,

Tony
Important to note some references you may have may quote in knots, while the IAS in `our` Comanche is in MPH.

But all pedantry aside, while the numbers are a useful ground exercise and give indications, it's what is going on in the air that matters - temperature, pressure, wind speed and direction all have a more significant effect on the aircraft, so relying on exactitudes in aviation is what gets people killed. It is, as you say, practice that makes perfect - and what the sim is perfect at.

Create a flight scenario with the Comanche at final approach, then load it again and again, altering speeds, loads, techniques and weather until you feel you have mastered any and all combinations including short field, wet and long grass, long tarmac runways, steep and shallow approaches.

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Scott - A2A
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Re: Weight & Balance and Landing Speed - Piper Comanche

Post by Scott - A2A »

Tony,

Comanche pilots and owners struggle with this all the time, as speed control is narrow with such a big wing. I would try coming over the fence at 90 mph, then another time at 80mph and feel how different it is to setup your flare at those speeds. And find the speed you are comfortable with at various airports.

Scott.
A2A Simulations Inc.

TonyW
Airman First Class
Posts: 70
Joined: 03 Jan 2016, 17:22

Re: Weight & Balance and Landing Speed - Piper Comanche

Post by TonyW »

Thanks Scott &b Malcott,

If I quoted Kts then that was an error as I know this aircraft uses MPH. I know most use Kts but I know that one or two of the default are in MPH and I have another addon that shows Km/h (which I can easily relate to from my car), so can be confusing. In any case I generally keep an eye on the white arc when on approach. As regards wind I generally make things easy for myself by setting just 8Kts and keep it close to the runway heading I'm using, and all flights are usually between sea level and 5,000ft.

I've now set up a saved flight specifically for landing practise and am keeping it separate from the Comanche that I using for my ongoing tour.

Regards,

Tony

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