Max Weight of Non Lift Producing Components

At 01:59 08 December 2017, Dan Daly wrote:
On Thursday, December 7, 2017 at 7:27:02 PM UTC-5, Jim wrote:
I admit I am baffled by "max weight of non-lifting parts". I
understand
=
the issue of spar bending moment limits, and I think I understand that
weig=
hing a glider without its wings will give the current non-lifting (i.e.,
no=
n-wing) weight, but I have a feeling there are subtle things here that I
do=
not understand.

I've rigged an ASK-21 and its wings are HEAVY! I haven't weighed
them
so=
I don't know just how heavy they are though. Certainly felt like more
tha=
n 100 lbs each. Ask me how I know. I'll guess (I know, don't guess)
each
=
wing weighs 150 lbs. Likely more. If I subtract 300 lbs from 780 and
then=
subtract that result from 1320 I'm still short of 902 - which I suppose
is=
a good thing.
=20

Glider cockpit load limits are set by the lowest value determined by:
Max AUW
Seat strength limits
Max wt of non-lifting parts
Forward CG limit

For a ASK21 for which I have the actual weighing results:
Max AUW 1320 lbs
Empty weight, fully equipped, 884 lbs
Therefore disposable load is 436 lbs
Seat strength limit is 242 lbs, so with a max weight pilot the other pilot

cannot exceed 194 lbs

Each wing weighs 219 lbs, max weight of non-lifting parts is 904 lbs.
Fuselage, tailplane, etc wt is 884 - 438 = 446 lbs. Hence max load
considering only non-lifting parts limit is 904 - 446 = 458 lbs. The AUW

limit takes precedence.

On this aircraft forward CG limit did not determine max cockpit load.
Min cockpit load is set by aft CG limit.

On Thursday, December 7, 2017 at 6:27:02 PM UTC-6, Jim wrote:
I admit I am baffled by "max weight of non-lifting parts". I understand the issue of spar bending moment limits, and I think I understand that weighing a glider without its wings will give the current non-lifting (i.e., non-wing) weight, but I have a feeling there are subtle things here that I do not understand.

For example, the ASK-21 POH lists the following weights:

Empty weight: approx 780 lbs
Max all-up weight: 1320 lbs
Max weight on non
lift producing members: 902 lbs

I've rigged an ASK-21 and its wings are HEAVY! I haven't weighed them so I don't know just how heavy they are though. Certainly felt like more than 100 lbs each. Ask me how I know. I'll guess (I know, don't guess) each wing weighs 150 lbs. Likely more. If I subtract 300 lbs from 780 and then subtract that result from 1320 I'm still short of 902 - which I suppose is a good thing.

Oh well. This all just makes my head hurt. Maybe what I should be doing is adding the weight of pilots, water, parachutes, etc. to 780 to ensure that the total is not beyond 1320. I suppose I already do this when I use Foreflight to calculate W&B.

TIme for a nap.

Max weight of non-lifting parts;
Maybe it's listed that way to prevent the rationalization "the useful load is less than I want, I will use some of the water ballast allowable weight to justify excess pilot weight, and still be under max gross"

Nobody would do that would they? ;-)

From the BGA:

5. Non-Lifting Parts. For sailplanes where the Leading Particulars specify a maximum weight
of non-lifting parts, it will additionally be necessary to weigh the wings to enable the weight of the
fuselage and tailplane to be calculated; this is the empty weight of non-lifting parts.


I can't say what the significance of exceeding the max would be, but from general life experience exceeding the max of anything is usually a bad idea.

RC

Le jeudi 30 novembre 2017 05:39:23 UTC+1, a écritÂ*:
From the BGA:

5. Non-Lifting Parts. For sailplanes where the Leading Particulars specify a maximum weight
of non-lifting parts, it will additionally be necessary to weigh the wings to enable the weight of the
fuselage and tailplane to be calculated; this is the empty weight of non-lifting parts.


I can't say what the significance of exceeding the max would be, but from general life experience exceeding the max of anything is usually a bad idea.

RC

Exeeding max weight of non-lifting parts makes you exceeding the structural limits of the plane (i.e. you start eating up the safety factor of 1.5), which is generally acknowledged as being a fairly stupid idea.

MTOW is not really connected to max weight of non-lifting parts.

While studying for my Flight Engineer license back in the 70s (do they
have Flight Engineers any more?), it was explained that the max weight
of non lifting components had to do with the strength (bending moments)
of the wing spar.Â* Help us out here, Steve L.

MTOW has, I believe, to do with landing gear, brakes, tires, etc. Think
MV**2 during an aborted takeoff.Â* Higher weight - higher takeoff speed
- WAY higher energy to dissipate, that V squared component.

On 11/30/2017 2:40 AM, Tango Whisky wrote:
Le jeudi 30 novembre 2017 05:39:23 UTC+1, a écritÂ*:
From the BGA:

5. Non-Lifting Parts. For sailplanes where the Leading Particulars specify a maximum weight
of non-lifting parts, it will additionally be necessary to weigh the wings to enable the weight of the
fuselage and tailplane to be calculated; this is the empty weight of non-lifting parts.


I can't say what the significance of exceeding the max would be, but from general life experience exceeding the max of anything is usually a bad idea.

RC
Exeeding max weight of non-lifting parts makes you exceeding the structural limits of the plane (i.e. you start eating up the safety factor of 1.5), which is generally acknowledged as being a fairly stupid idea.

MTOW is not really connected to max weight of non-lifting parts.

--
Dan, 5J

I believe you are correct, you don't want to overload the spar with fuselage weight, thus, spread it out through the wings.
I know some ships had water in the wings but also additional in a tank in the fuselage to get the wing loading up due to low volume wings. You would load the wings, then finish off with the fuselage. Dumping ballast is fuselage first, then wings.

As to MTOW, some larger aircraft also have a MLW, max landing weight which I believe is mostly due to loads when the mains hit the runway.
So, some aircraft can take off at a higher weight than they can land! So, if they run into an issue, they may have to fly around to burn fuel off to get within landing weight, or even dump fuel (don't tell the EPA!).

Screw the EPA!Â* When I was doing engine out maintenance recovery
flights, it was standard practice to open all the tank dump valves
before take off leaving only the wing tip nozzle valves to start fuel
dumping.Â* That might save a second or two should the situation become
critical.

On 11/30/2017 8:56 AM, Charlie M. (UH & 002 owner/pilot) wrote:
I believe you are correct, you don't want to overload the spar with fuselage weight, thus, spread it out through the wings.
I know some ships had water in the wings but also additional in a tank in the fuselage to get the wing loading up due to low volume wings. You would load the wings, then finish off with the fuselage. Dumping ballast is fuselage first, then wings.

As to MTOW, some larger aircraft also have a MLW, max landing weight which I believe is mostly due to loads when the mains hit the runway.
So, some aircraft can take off at a higher weight than they can land! So, if they run into an issue, they may have to fly around to burn fuel off to get within landing weight, or even dump fuel (don't tell the EPA!).

--
Dan, 5J

On Thursday, November 30, 2017 at 8:44:24 AM UTC-7, Dan Marotta wrote:
While studying for my Flight Engineer license back in the 70s (do they
have Flight Engineers any more?), it was explained that the max weight
of non lifting components had to do with the strength (bending moments)
of the wing spar.Â* Help us out here, Steve L.

MTOW has, I believe, to do with landing gear, brakes, tires, etc. Think
MV**2 during an aborted takeoff.Â* Higher weight - higher takeoff speed
- WAY higher energy to dissipate, that V squared component.
Dan,
No more flight engineers. You have to go back to 727s or early 747s to find a Flight engineer panel and all of those have been retired in this country years ago. MTOW is based on 5 different Performance charts (4 of which are based on engine out performance). MLW is based on Landing Gear and brake energy. Zero Fuel Weight is based on bending moment just like you said. I checked with the factory on my glider and yes, Non Lifting is just like Max Zero Fuel WT is on a jet. Everything beyond this must be wing ballast.

The weight of the wings should not change much from the factory weight
until
repairs or refinishing.

In the fuselage, instruments, batteries, O2 system, pilot, chute,
documents,, tie
down kit, lunch and drinks need to be included.

It all adds up.

Northwest Airlines hated it when they got ride of the flight engineer, less people to play drinking games with all night before flight.

On Thursday, November 30, 2017 at 11:55:47 AM UTC-8, K m wrote:
On Thursday, November 30, 2017 at 8:44:24 AM UTC-7, Dan Marotta wrote:
While studying for my Flight Engineer license back in the 70s (do they
have Flight Engineers any more?), it was explained that the max weight
of non lifting components had to do with the strength (bending moments)
of the wing spar.Â* Help us out here, Steve L.

MTOW has, I believe, to do with landing gear, brakes, tires, etc. Think
MV**2 during an aborted takeoff.Â* Higher weight - higher takeoff speed
- WAY higher energy to dissipate, that V squared component.
Dan,
No more flight engineers. You have to go back to 727s or early 747s to find a Flight engineer panel and all of those have been retired in this country years ago. MTOW is based on 5 different Performance charts (4 of which are based on engine out performance). MLW is based on Landing Gear and brake energy. Zero Fuel Weight is based on bending moment just like you said. I checked with the factory on my glider and yes, Non Lifting is just like Max Zero Fuel WT is on a jet. Everything beyond this must be wing ballast.