Max Weight of Non Lift Producing Components

So what does the main pin(s) count as?

KN

At 16:07 30 November 2017, Tony wrote:
We weighed everything together and then the wings. Felt that was easier
than trying to hold the fuselage with tail attached upright and on the
scales.

On 11/30/2017 9:53 AM, Kevin Neave wrote:
So what does the main pin(s) count as?

KN

At 16:07 30 November 2017, Tony wrote:
We weighed everything together and then the wings. Felt that was easier
than trying to hold the fuselage with tail attached upright and on the
scales.

Try flying without it/them in place and get back to the group how it went!

More seriously, and structurally, it/they are part(s) of the wing.

Bob W.

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Part of the wings, yes, but certainly not lift generating.Â* But you
can't do without them...

On 11/30/2017 10:15 AM, BobW wrote:
On 11/30/2017 9:53 AM, Kevin Neave wrote:
So what does the main pin(s) count as?

KN

At 16:07 30 November 2017, Tony wrote:
We weighed everything together and then the wings. Felt that was
easier than trying to hold the fuselage with tail attached upright
and on the scales.

Try flying without it/them in place and get back to the group how it
went!

More seriously, and structurally, it/they are part(s) of the wing.

Bob W.

---
This email has been checked for viruses by AVG.
http://www.avg.com


--
Dan, 5J

BGA has a concession which allows for non-aerobatic flights to exceed the maximum weight of non-lifting parts by 3%, so my that margin it should be fine.

Does anyone know, how exceeding that non-lifting weight influences the flutter of the wing?

Stefan

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

No, it doesn't influence flutter. Flutter is controlled by the eigenfrequencies of the wing.

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.

On Thursday, November 30, 2017 at 9:00:07 AM UTC-8, Kevin Neave wrote:

So what does the main pin(s) count as?

Very incisive question! That's a good demonstration of how the mass of non-lifting is a reasonable metric for the approximation of wing main spar maximum bending moment, but is still just an approximation.

At issue is that using a maximum mass of non-lifting parts to limit the wing spar bending moment is only valid when any mass added to the wings is distributed spanwise according to the wing lift distribution. So if for whatever reason you add a bunch of mass to the inboard ends of the wings (depleted uranium root ribs maybe?), you can be within the allowable non-lifting mass and within the load factor envelope, but still develop excessive wing spar bending moment.

Bottom line: Respect mass limits to the spirit and the letter of the published values. And if you want a glider with lots of non-lifting mass margin, build an HP-24. The one we finished last summer has an empty non-lifting mass of ~220 lbs (ready to fly with batteries, instruments, 24 ft^2 O2 bottle, etc) and a maximum of ~605 lbs, yielding a payload of ~385 lbs for pilot, parachute, FES, electric self-launch, BRS, etc.

--Bob K.