Range max payload

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joefremont
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Range max payload

Post by joefremont » Mon Mar 22, 2021 7:25 pm

We just added to the database the CRJ-700ER and CRJ-700LR, one of the challenges for these aircraft is that most sources, including the manufacturer, list the range with max payload rather than the range with max fuel, and we need the range with max fuel. One interesting thing about the the three CRJ-700 variants, is they have the same empty weight, max payload and fuel capacity, its really only the MTOW that is different. So with zero payload and max fuel, they would fly the same distance. While with max payload the ranges are 1,440 nm for the 700, 1,739 nm for the ER and 2,011 nm for the LR.

This got me thinking, should we add range with max payload to the data we keep for each airplane? Then we could warn pilots when they load an aircraft up to its MZFW and book a flight for beyond the range with max payload, or even flag as suspicious when they fly further than that with max payload.


The hard part of course would be finding all the data for the aircraft we already have.
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Re: Range max payload

Post by BVU-951 » Wed Mar 24, 2021 5:00 pm

Good Idea Joe, I have all those figures on a spread sheet, but would help others who can't work these things out.
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Re: Range max payload

Post by Zehvra » Wed Mar 24, 2021 9:47 pm

That would be very helpful Joe

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Re: Range max payload

Post by joefremont » Thu Apr 08, 2021 5:48 pm

I did some more reading on this, I think the problem can be described in this graph.

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This is an example/description of a normal range chart for an aircraft, based on that we would probably need three numbers.

1) Range max payload
2) Range MTOW
3) Range zero payload

Finding the data for this may be difficult and in my general searching that sort of data is not in specifications listed on websites or general references. You would really need to find the pilot manuals or other technical references to figure it out. I don't have the time to look this up but if others are willing to commit to doing the work we can consider it.
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Re: Range max payload

Post by BVU-951 » Fri Apr 09, 2021 1:19 pm

joefremont wrote:
Thu Apr 08, 2021 5:48 pm

1) Range max payload
2) Range MTOW
3) Range zero payload
Example:-

R=max nm
F=max fuel weight
W=max Take off Weight
M= max Zero fuel weight

Range max payload = R/F x (W-M)

R, F, W & M are all given in the aircraft data.

Hope I am being helpful
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Re: Range max payload

Post by joefremont » Fri Apr 09, 2021 7:03 pm

Hi Alan, I just did a quick look at the data in the DB using your formula, it's not bad but I suspect the real world numbers are not quite so linear and for aircraft where it's impossible to get numbers it would probably a starting point.

Some manufacturers have a listed MZFW which is the same as the MTOW (cessna for one) so it may be difficult.
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Re: Range max payload

Post by BVU-951 » Fri Apr 09, 2021 10:35 pm

I just use it to work out where I have to stop for fuel, if I am fully loaded to go long distance, I haven't had a problem in 10 years. Not so important now you can divert.

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Re: Range max payload

Post by BVU-951 » Sat Apr 10, 2021 8:44 pm

joefremont wrote:
Fri Apr 09, 2021 7:03 pm

Some manufacturers have a listed MZFW which is the same as the MTOW (cessna for one) so it may be difficult.
This can't be true Joe, you would never be able to take off.
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Re: Range max payload

Post by joefremont » Sat Apr 10, 2021 11:54 pm

BVU-951 wrote:
Sat Apr 10, 2021 8:44 pm
joefremont wrote:
Fri Apr 09, 2021 7:03 pm

Some manufacturers have a listed MZFW which is the same as the MTOW (cessna for one) so it may be difficult.
This can't be true Joe, you would never be able to take off.
You could never take off if your ZFW was the MZFW true.

https://cessna.txtav.com/en/piston/cess ... odel-specs

This is the ever popular Cessna 172.

Go down to the weights, they don't show MZFW but do show:

WEIGHTS
Maximum Ramp Weight 2,558 lb (1,160 kg)
Maximum Takeoff Weight 2,550 lb (1,157 kg)
Maximum Landing Weight 2,550 lb (1,157 kg)
Usable Fuel Weight 318 lb (144 kg)
Usable Fuel Volume 53 gal (201 l)
Basic Empty Weight 1,680 lb (762 kg)
Useful Load 878 lb (398 kg)
Maximum Payload 870 lb (395 kg)
Full Fuel Payload 560 lb (254 kg)

Note that full fuel payload is different than maximum payload so when they say 'payload' they mean non fuel payload, and if you add Basic Empty Weight (762kg) to Maximum payload (395kg) it equals 1,157 kg, same as the MTOW.

I took a look at some of the other Cessna's and while most of the others show different MLW and MTOW the empty weight plus max payload is always equal to the MLW meaning no reserve fuel.
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Re: Range max payload

Post by BVU-951 » Sun Apr 11, 2021 11:41 am

I have just copied and pasted for the 172

Max Zero Fuel Weight 1111 kg
Max Take Off Weight 1157 kg
Max Landing Weight 1157 kg
Max Fuel Weight 212 kg
Cargo Space 180 kg
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Re: Range max payload

Post by BVU-951 » Sun Apr 11, 2021 7:34 pm

joefremont wrote:
Sat Apr 10, 2021 11:54 pm
BVU-951 wrote:
Sat Apr 10, 2021 8:44 pm
joefremont wrote:
Fri Apr 09, 2021 7:03 pm

Some manufacturers have a listed MZFW which is the same as the MTOW (cessna for one) so it may be difficult.
This can't be true Joe, you would never be able to take off.
You could never take off if your ZFW was the MZFW true.

https://cessna.txtav.com/en/piston/cess ... odel-specs

This is the ever popular Cessna 172.

Go down to the weights, they don't show MZFW but do show:

WEIGHTS
Maximum Ramp Weight 2,558 lb (1,160 kg)
Maximum Takeoff Weight 2,550 lb (1,157 kg)
Maximum Landing Weight 2,550 lb (1,157 kg)
Usable Fuel Weight 318 lb (144 kg)
Usable Fuel Volume 53 gal (201 l)
Basic Empty Weight 1,680 lb (762 kg)
Useful Load 878 lb (398 kg)
Maximum Payload 870 lb (395 kg)
Full Fuel Payload 560 lb (254 kg)

Note that full fuel payload is different than maximum payload so when they say 'payload' they mean non fuel payload, and if you add Basic Empty Weight (762kg) to Maximum payload (395kg) it equals 1,157 kg, same as the MTOW.

I took a look at some of the other Cessna's and while most of the others show different MLW and MTOW the empty weight plus max payload is always equal to the MLW meaning no reserve fuel.
In this case they are advertising a trainer, so they give the max weight of pupils you can put in this aircraft to demonstrate the controls of the aircraft. For it to take off, with full fuel 310 lbs of flesh will have to get off.

The data that exists in FSAirlines, I think is good enough. Probably not being very helpful with what you are trying to achieve.
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Re: Range max payload

Post by Cat » Sun Apr 11, 2021 8:58 pm

Many of the GA manufacturers use "juiced numbers" to show their product is better than it really is. Yes it can fly X distance and yes it can carry Y payload, but then you have to dig into the fine print to see what the true max distance is with max payload or the max payload with max distance.

Just like they tend to announce top cruise speeds in mph to make them look faster.

Marketing 101

Beware of "useful load" numbers as that usually includes some sort of fuel quantity as well, it does not always mean actual "pay" load. Many small aircraft have such numbers in their specification pages and one must really look at two things: empty weight + fuel (trip and reserves) = what I call my Operating Weight - Now take the MTOW and subtract my operating weight and I come up with the maximum weight I can stuff in it at departure.

This does not mean it will be safe to land! Some aircraft specs, like the Cessna 208 Caravan EX for one, have a max landing weight that is very close to MZFW which means if you pack it to the MZFW number in FSAirlines, you will have to land on fumes and you can only load a few hundred pounds of fuel before you hit MTOW. So again, the specs look great but in reality no one truly flies 208's loaded to MZFW as you wouldn't have enough fuel to go anyplace other than up the road a few minutes. So the solution is to either throw out generic cargo after loading the fuel you need OR limiting the cargo weight in the aircraft seat configuration tool. The problem arises when pilots fill up on package cargo because they are not allowed to throw out package cargo for fuel prior to departure.
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