Structural Sub-Component Weight Groups
Parametric Plots
The
plots below show
some of the
preliminary parametrics for the sub-component weights that sum to the
Overarching Structural Group weight that have been developed from the
data
available for single engine monoplane WWII era aircraft discussed on
this website.
Caveats
Please
note
that;
- Currently
everything is still
very much a work in progress and subject to further refinement and
revision as I work to verify the data that I have currently transcribed
from the references, and as I work to collect dimensional and powering
data on the specific aircraft that I have weight data for.
- All weight
units are in pounds and power units are in Horsepower.
- For some
weight groups (such as the "Tail" group or the
"Landing Gear" group, a further subdivions of weights may be provided
for those airplanes where such data was available. As such,
rows
below the "Tail" group for the "H Tail" (Horizontal Tail) and "V Tail"
(Vertical Tail) are included for some aircraft. Similarly
rows
below the "Landing Gear" group for "Main LG" and "Tail/Nose Aux LG"
have also been added, though I may eventually separate the "Tail/Nose
Aux LG" row into a separate "Nose Aux LG" and "Tail Aux LG" row to make
it easier to differentiate these weights on the parametric plots being
developed.
- It
currently is unclear what all is included in the "Engine Section"
weight group. It appears that this includes the the engine
mounts
for allaircraft as well as cowling and cooling flaps for radial
engines. However for a few aircraft in the lists below such as the
XP-63A a very low value of 4lb is given, while for the P-63A-10 and
P-63C no value is given, leading to the suspicion that the weights of
the enine mount for those aircraft may be included elsewhere in the
weight estimate (such as in the "Fuselage" weight or "Engine
Accessories" weight groups.
- I need to
further review and
clean up the "Fuselage" and "Body" group weights to ensure that I have
correctly and consistantly recordedd this data. Specifically;
- In
Reference [1] many of the aircraft list "Fuselage" and "Engine Section"
weights separately. However for several of the F2A/B339
aircraft
variants a "Body + Landing Gear" weight and an "Engine Section" weight
is given, whereas for the XF2A-1 no separate "Engine Section" weight
appears to be given.
- In
Reference [2] only "Body" weights are listed, with no mention of
"Fuselage" or "Engine Section" weights.
- In
References [3] and [4] the "Body Group" weight is listed as including
the "Fuselage less Engine Section" and "Alighting Gear" (Landing Gear).
However, since weight data is provided for both the
"Fuselage less Engine Section" and "Alighting Gear" in addition to the
total "Body Group" weight it is fairly easy to re-align these weights
to match the format used in other references if necessary.
However, eventhough the "Fuselage less Engine Section" is
called
out as a weight group I cannot find anywhere in these references where
the "Engine Section" is accounted for. As such, I am
currently
still reviewing the weight from these two references and have not yet
incorporated them into the plots below.
- In
Reference [5] the "Body Group" weight and "Landing Gear" weights are
listed separately.
As such, it appears that the
most consistent use of terminology would be to;
- Treat the
"Body Group" as being the sum of the "Fuselage" and "Engine Section
Groups"
- Investigate
the weights of the "Alighting Gear" (Landing Gear) separately, where
possible
- Also
dosome analyses of "Body" weight plus "Landing Gear" weight to see how
the F2A/B339 variants listedin Reference [1] compare to the other
aircraft that there is data on.
Beyond this I also
intend to continue to review the information provided in References [3]
and [4].
Structural
Weight Sub-Components
As
noted on
the General
Weight
Summary Format page,
the overarching Structural Weight Group is equal to
the sum of the;
- Alighting/Landing
Gear Group
The
first plot below show the relationship of Wing Weight to Total
Wing
Area. As shown in this plot a number of the naval aircraft
designs have folding wings.
I am
currently working to try and
develop more detailed plots to better help identify the impact that
incorporating the ability to fold has on the overall weight of a wing.
In addition, in reviewing Wing Weight equations for other
aircraft type it can be seen that there are several other factors other
than just Wing Area which are expected to impact the overall wing
weight, including such factors as;
- Wing Area
- Weight of
Fuel Carried in the Wings
- Wing
Aspect Ratio
- Wing
Sweep Angle
- Wing
Taper Ratio
- Wing
Thickness to Chord Ratio
- Ultimate
Load Factor
- Aircraft
Design Gross Weight
- Dynamic
Pressure - which is a factor of the aircraft's speed
In the
paper "A Review of Aircraft Wing Mass Estimation Methods" by Odeh
Dababneh amd Timoleon Kipouros, a figure is provided for more modern
aircraft plotting Wing Weight versus a parameter equal to;
The Aircraft's
Gross Weight * Ultimate Load Factor (in G's) * Wing Span * Gross Wing
Area / Wing Thickness @ the Root
Plotting the weight information available for WWII era Aircraft against
the same parameter (assuming
pounds for weight and feet or feet squared for the other dimension, as
appropriate) results
in the plots shown below, where the first graph shows the data on a
log-log scale and the second plot shows the data on normal X and y
scales.
In these graphs please note that aircraft with fixed wings are shown as
solid symbols while those with white centers represent aircraft with
foldable wings. As shown in these figures although there is some
scattter the fixed wing data shows a reasonable fit (R2=
0.9043) with the data
for aircraft showing a slightly weaker fit (R2=
0.7708). However, it should be noted that some assumptions were
made in the data. Specifically;for aircraft where
- a Design Weight and
Ultimate load Factor was available those were used
- a Design Weight was
not known, the Basic Gross Mission Weight was used
- the Root Thickness
was known that was used, but where it was not known it was estimated
from the Root Chord Length and nominal Root t/c data
- the Ultimate Load
Factor is known for one variant, it was assumed to be the same for
other variant
Additionally,
for the Brewster 239v/XF2A-1 Prototypes, where a Normal Design Load
Factor of 9 G's is known and a ration of Ultimate to Yeild Strngth of
1.35 is also provided, the Ultimate Load Factor was assumed to by 12.15
G's (or 1.35 * 9 G's).
Some concerns here are that;
- It is not fully clear that Design Weight and Basic Gross Mission Weight are the same
- the nominal Root t/c listed for a
given airfoil may be rounded to the nearest %, and as such Root Chord *
Root (t/c) may vary by a small amount from the actualnominal Root Wing
Thickness
- It is
possible that for diffeertnet variants of an aiurcraft that the
Ultimate Load Factor may be reduced as the aircraft weight increases.
With respect to the Ultimate Load Factors for different variants of an
aircraft, it is noted that in Ref X for the Curtiss Hawk H-75A when
fitted with a Curtiss Wright Cyclone Engine having a Basic Gross
Mission Weight o 5562lb is listed as having an Ultimate Load Factor of
12 G's, while the dsame design, but fitted with a Pratt & Whitney
Twin Wasp engine and having a Basic Gross Mission Weight of 5792lb is
listed as having an Ultimate Load Factor of 11.5 G's (where 5562lb * 12
G's ~= 5792lb * 11.5 G's).
The next
three plots show some of the areas that I have been looking into with
respect to this. The first two graphs show a plot of the Total
Wing Weight of the designs being analyzed divided by the their Total
Wing Area (which includes the ailerons and flaps) versus Basic Gross
Mission Wt and Design Speed Limit, respectively. As
shown in these plots there is a trend of increasing Wing Wt/Square Foot
with increasing Basic Gross Mission Weight and Design Speed Limit,
which is a factor of the wings having to support more lift and them
experiencing more dynamic forces as both weight and speed increase.
Please
note that in the second plot above Design Speed Limit is not the
maximum speed that the plane could reach at full power,
but rather a maximum speed that is used during the design of an
aircraft to help determine the maximum forces and loads that the
structure will experience. Unfortunately, from data on the P-51D it
appears that this may notbe the same as the "Not To Exceed" or "Never
Exceed" Speed that is sometimes
listed for aircraft. Since I currently do not have data on
Design Speed
Limits or Not to Exceed Speed Limits for all the aircraft currently
being analyzed, I have also put together an additional plot of Wing
Weight/Square Foot versus the Rated Take-Off Power of the installed
engine on each plane the to see if that parameter could be used as a
stand in, since for these single engine monoplanes currently being
analyzed, as a plane with higher installed power will likely
have a higher top end speed,and as such would likely also have a higher
Design Speed or Do Not Exceed Speed.
These
plot represent an initial first step in the analyses of Wing Wt for
these aircraft and I hope to continue looking into Wing Wt in the
future.
The
next three plots
show the
relationship of Total Tail Weight to Total Tail Area, Horizontal Tail
Weight to Horizontal Tail Area, and Vertical Tail Weight to Vertical
TailArea, respectively.
These
last few plots show "Body Group" weight versus both "Basic Mission
Gross Weight" and "Body Length". In reviewing the data
though, it
is not clear what the "Body Length" reported in Reference [2]
specifically relates to. Specifically for radial engined
aircraft
it looks like it may actually only address to length of the aircraft
aft of the fire wall, and not include the length of the cowling.
As such I intend to further review these values and may
eventually replace the plot below with a plot of "Body Weight" versus
"Total Aircraft Length". Also along these lines, since there
appears to be some degree of scatter in the plot of "Body" weight verse
"Body Length" I may look to trying to also incorporate "Body Width"and
"Body Depth" into the analyses since the weight of a very deep fuselage
or a very narrow fuselage may be expected to vary a fair bit from other
aircraft of similar lengths.
The
next three plots show the Total Landing Gear Weight, the Main Landing
Gear Weight, and the Nose/Tail Landing Gear Weight as a function of the
Basic Mission Gross Weight of the aircraft analysed.
Notes:
This website
has been developed with a number of low cost or free programs including
Hot Metal Pro, KompoZer, Microsoft
Designer and Da Button
Factory.com
Rev 4-28-26