Aeronautical Engineer required part time

#1
The task will suit a retired Aeronautical or Structural Engineer and involves checking, optimising and testing the structural integrity of a light sport aircraft design. The task includes the application for LSA status under the RAAus and CASA. Work at your own pace. Sydney based.
Please contact Ray on 0414 559742
 
#3
My basic calcs show the aircraft is waaayy over strong! It would be nice to optimise the structure
for say 750 Kg's MTOW @ +4,-2 G's taking the strongest parts from 544Kg/600Kg @ +6,-4G loadings.
Will have to test things like engine mounts, battery box and tailplane mounts, etc.
 

bexrbetter

Well-Known Member
#4
Practical changes:

25 x 2mm longerons from the pax rearwards.
All 25 x 3mm vertical, lateral and angle braces to the thinner gauge used.
All 0.025" sheets to 0.020".
Aluminium ribs rather than the fiberglass ones.
Titanium HS spar.
10kg landing gear too heavy (and get it out of the airstream).

I'll send you my bill.

What you really need to do is get your build manuals and service together, not much wrong with the product.

You're welcome.
 
#5
My basic calcs show the aircraft is waaayy over strong! It would be nice to optimise the structure
for say 750 Kg's MTOW @ +4,-2 G's taking the strongest parts from 544Kg/600Kg @ +6,-4G loadings.
Will have to test things like engine mounts, battery box and tailplane mounts, etc.
Practical changes:

25 x 2mm longerons from the pax rearwards.
All 25 x 3mm vertical, lateral and angle braces to the thinner gauge used.
All 0.025" sheets to 0.020".
Aluminium ribs rather than the fiberglass ones.
Titanium HS spar.
10kg landing gear too heavy (and get it out of the airstream).

I'll send you my bill.

What you really need to do is get your build manuals and service together, not much wrong with the product.

You're welcome.
 
#6
Thanks Bex,
Yes, once the calculations are done for the structural optimisation I'm sure there will be some changes.
It seems to me that the rear vertical diagonals are in compression instead of tension which is ok if you have thick walls.
Titanium landing gear perhaps?!
Build manual is coming along. Service... well it is not up to me to judge.
I like your idea for the ribs.

Always open to ( not rude) suggestions!
Regards,
Ray
 

bexrbetter

Well-Known Member
#7
It seems to me that the rear vertical diagonals are in compression instead of tension which is ok if you have thick walls.
FEA says the rear diagonols are next to useless and do virtually nothing except help stabilise the gusset, and the corresponding opposite corner of the skin. That in turn stabilises the vertical, and stops oil canning, as long as you have filled the gap between it and the skin with silicone or other filling adhesive.

They do not need to be anything but lightweight tube for the purpose they serve. Think about it, 6 little rivets in each end, 3 per side, and you've never heard of a problem (?), so you can understand how little force they see.

Get an Engineer to crunch the numbers though, or do a load test.

The fiberglass ribs are certainly convenient for a taper wing, but heavy. You might want to put some typical lightening holes and strengthening ribs in them (have a look at a typical Vans rib for example).
 

bexrbetter

Well-Known Member
#8
It seems to me that the rear vertical diagonals are in compression instead of tension which is ok if you have thick walls.
FEA says the rear diagonols are next to useless and do virtually nothing except help stabilise the gusset, and the corresponding opposite corner of the skin. That in turn stabilises the vertical, and stops oil canning, as long as you have filled the gap between it and the skin with silicone or other filling adhesive.

They do not need to be anything but lightweight tube for the purpose they serve. Think about it, 6 little rivets in each end, 3 per side, and you've never heard of a problem (?), so you can understand how little force they see.

Get an Engineer to crunch the numbers though, or do a load test.

The fiberglass ribs are certainly convenient for a taper wing, but heavy. You might want to put some typical lightening holes and strengthening ribs in them (have a look at a typical Vans rib for example).
 

Geoff_H

Active Member
#11
I see the problem with getting a retired professional engineer to do the design work is professional indemnity insurance. The insurance only covers claims made from the year in which the engineering error was discovered. Claims can be made up until 7 years after the design was made, i.e.design now fault found 7 years then you are only covered if you have cover in that 7th year. At around $7k to 10k per year it means that it would cost me at least $50k to do such a job. Not worth it, and the liability cannot be off loaded by an agreement not to litigate, someone's family could litigate if you are dead. I suggest that you go to a consultant company, they will have PI and someone to check calculations.
 

Geoff_H

Active Member
#13
A divorce lawyer charges $700/hr, no promises, an engineering consultant charges around half this and must promise success or get sued by the guys that charge $700/ hr. Lawyers are the ones that have screwed it up for all of us. I love designing aircraft, doing my own aircraft at present, but it is too risky to do it for others. I cannot even sell the design of my aircraft.
 

Geoff_H

Active Member
#15
What about the fuel pump parts that caused the Jandakot crash? Fairly recent too. But also who wants to be the first. PI is a real problem for all engineers that consult.
 

Geoff13

Well-Known Member
#18
I see the problem with getting a retired professional engineer to do the design work is professional indemnity insurance. The insurance only covers claims made from the year in which the engineering error was discovered. Claims can be made up until 7 years after the design was made, i.e.design now fault found 7 years then you are only covered if you have cover in that 7th year. At around $7k to 10k per year it means that it would cost me at least $50k to do such a job. Not worth it, and the liability cannot be off loaded by an agreement not to litigate, someone's family could litigate if you are dead. I suggest that you go to a consultant company, they will have PI and someone to check calculations.
Is it possible in the case of a one of job to purchase PL Insurance to cover that job and only that job?
And if so would that then become viable?
 

Geoff_H

Active Member
#19
Yes it certainly would. I have involved with PI over the years and no broker has ever offered PI for a job. I usually get the company wanting my skills to get coverage from their PI insurer to cover me. It worked well.
 

fly_tornado

Well-Known Member
#20
but Ray is building experimental aircraft, the builder declares the airworthiness of the plane. I would cost millions to prove an aircraft designer was at fault.
 
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