WWI aircrafts G-loads

[Greybeard]

I wonder what could be G-loads of WWI era aircrafts. If they were part of specifications and were in some way checked. Both positive and negative. Are there some values available?

Thanks for any help.
GB

[YavorD]

Hi Greybeard,
A couple of documents can provide some information.
Regards,
Yavor

Dr. Adolf Rohrbach. NACA-TN-107 Structural Safety During Curved Flight
http://ntrs.nasa.gov/archive/nasa/ca...1993080905.pdf

REPORT ON THE STRENGTH OF THE WINGS OF CAPTURED GERMAN AEROPLANES.
By H. B. IRVING, B.Sc.
Reports and Memoranda (New Series), No. 350 July, 1917.

SUMMARY.---Stress calculation's were made on the following machines :-
Two-seater biplanes : Albatross C.III., Aviatik 1916, L.V.G. 1916,
Rumpler 1916.
Single-seater scouts : Albatros, D.I., Halberstadt.
The general conclusion arrived at from examination of the wings of
various German machines and from calculations is that, as regards the
main spars, German machines are decidedly below British machines in
strength; as regards the general structure of the wings, including ribs,
drag struts, drag wiring, trailing edges, etc., there does not seem to be
any decided difference in the strength and stiffness. The leading portions
of the wings of German machines are perhaps in general rather stiffer
than those of British machines.

http://naca.central.cranfield.ac.uk/...arc/rm/350.pdf

STRESS CALCULATIONS ON THE S.E.5 AEROPLANE
By L. W. Bryant, B.Sc., A.R.C.Sc., and H. B. Irwing, B.Sc.
Reports and Memoranda, No. 491 April, 1917.

SUMMARY.--The wings will bear 5½ times normal loading, but will
then fail under shear at a point in the front spar just inside the wing
strut connection. A strengthening of the upper wing spars at this point
would greatly increase the strength of the wing as a whole. The upper
wing spars are also weak for failure in a horizontal plane under compression.
The fuselage is much stronger relatively than the wings; it will
stand 25 lbs. per sq. ft. on the tail.

http://naca.central.cranfield.ac.uk/...arc/rm/491.pdf

ON THE POSSIBLE LOADING OF THE WINGS AND BODY OF AN AEROPLANE IN FLIGHT.
By L. W. Bryant, B.Sc., A.R.C.Sc.
Reports and Memoranda, No. 496 May, 1917.

SUMMARY.--Wing loads.--Maximum wing loading during a loop may
occur at any point from the bottom to the top of the loop on the upward
path with elevators and Controls as usually arranged. The greatest
'wing loads will not in general occur in flattening out from the limiting
speed, but at about 150 to 160 m.p.h. The front spar is most heavily
stressed when the critical angle is reached at a speed of about 160 m.p.h.,
and the rear spar when the speed is the limiting speed and the lift
coefficient about one-fourth of the maximum.
Body loads.--Greatest tail load occurs when the speed is a maximum
and the pilot's pull on the control lever is also a maximum. The rear
portion of the body is most heavily loaded when the tail load is greatest,
and the fore part when the centrifugal load and the total wing load are
each at their maximum.

http://naca.central.cranfield.ac.uk/...arc/rm/496.pdf

REPORT OF THE LOAD FACTORS SUB-COMMITTEE.
SCHEDULE OF LOAD FACTORS FOR HEAVIER-THAN-AIR CRAFT.
Reports and Memoranda, No. 673. January 6th, 1920.

http://naca.central.cranfield.ac.uk/...arc/rm/673.pdf

[Pfalz-Scout]

Originally Posted by Greybeard

I wonder what could be G-loads of WWI era aircrafts. If they were part of specifications and were in some way checked. Both positive and negative. Are there some values available?

Thanks for any help.
GB

Hello Greybeard,

yes there are. In Germany the IDFLIEG established the Bau- und Liefervorschriften (BLV) –this means the construction and delivery regulations. Each new German aircraft was evaluated in accordance with these regulations at Adlershof before release of serial production. The load test was a part of this type test. This static load test was performed by placing sand bags on the wing structure. The whole sand bags weight was the sum from the airplane and the payload. The fuselage was supported in the appropriate flight attitude. The structure has to fulfil a factor of safety. The factors as stated below were for E- and D type airplanes only:
Fall A: pulling out of a dive, load factor 5
Fall B: gliding flight in an angle of 30 degrees, factor 3,5
Fall C: vertical dive, factor 2,5
Fall D: load on the first fifth of the wings chord during Fall B, factor 3.
Fall D was an virtual value and normally not checked.
Additional there were also loads for the rudder, elevator ailerons and the control stick.
For the ailerons: It must be able to care a load of 150kg to 200kg per square meter
For the rudder and elevator: 300kg per square meter
The control stick has to withstand a load of 80kg to 100 kg.

Regards
Pfalz-Scout

[YavorD]

Hi Pfalz-Scout!
The norms obviously were developed during the war, and re-evaluated after the war, as it was shown in an article written by one of leading Zeppelin-Staaken engineers:

Dr. Adolf Rohrbach. NACA-TN-107 Structural Safety During Curved Flight
http://ntrs.nasa.gov/archive/nasa/ca...1993080905.pdf
...
The factors of safety first required by the B.L.V. (military specifications) in 1916 (Table 1) were modified in 1918 (Table 2) on the basis of the enormously increased experience. The safety factors for the most maneuverable airplanes were raised considerably, while they were somewhat lowered for giant airplanes. It is probably true that the safety factors of the 1918 B.L.V. military airplanes were just large enough to guarantee the wings against breaking.
...

Regards,
Yavor

[Pfalz-Scout]

Originally Posted by YavorD

Hi Pfalz-Scout!
The norms obviously were developed during the war, and re-evaluated after the war, as it was shown in an article written by one of leading Zeppelin-Staaken engineers:



Regards,
Yavor

Hello Yavor,
Yes, you are right. My source is a book from July 1917, obviously based of the BLV data from 1916, valid for classified airplanes. Table 2 of technical note No.107 shows us more the examination in accordance with weight and payload instead the former typical classification of E-D, C-G and R airplanes.
Thank you for pointing out.

Best Regards
Pfalz-Scout

[Taz]

GB- Hadingham in The Fighting Triplanes reports the Sopwith Triplane being able to pull loads of 4.5 g for 10 seconds and 6 g for 4-5 seconds, measured from the turn radius. Available energy was often quite low on WW-I aircraft and even maximum effort on the flight controls could only pull fairly low g loads. High g turns were unbelievably tight because of the low speeds involved but faded rapidly as velocity decreased because of the g forces acting like a huge speed brake. Hence the very short time period the Sopwith Triplane could sustain high g before airspeed bled down.

Taz
Terry Phillips

[Greybeard]

Thank you to all for invaluable help.

GB