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152 AFDD Weight Models<br />
19–2 Rotor Group<br />
The rotor group consists of: blades, hub and hinge, spinner, and blade fold structure. The blade<br />
and hub-hinge weights for the AFDD82 model are:<br />
wblade =0.02606NrotorN 0.6592<br />
blade R 1.3371 c 0.9959 V 0.6682<br />
tip ν 2.5279<br />
blade<br />
whub =0.003722NrotorN 0.2807<br />
blade R 1.5377 V 0.4290<br />
tip ν 2.1414<br />
hub (Wblade/Nrotor) 0.5505<br />
Wblade = χbladewblade<br />
Whub = χhubwhub<br />
Based on 37 aircraft, the average error of the blade equation is 7.7% (fig. 19-2). Based on 35 aircraft,<br />
the average error of the hub equation is 10.2% (fig. 19-3). The blade and hub-hinge weights for the<br />
AFDD00 model are:<br />
wblade =0.0024419ftiltNrotorN 0.53479<br />
blade R 1.74231 c 0.77291 V 0.87562<br />
tip ν 2.51048<br />
blade<br />
whub =0.18370NrotorN 0.16383<br />
blade R 0.19937 V 0.06171<br />
tip ν 0.46203<br />
hub (Wblade/Nrotor) 1.02958<br />
Wblade = χbladewblade<br />
Whub = χhubwhub<br />
where ftilt =1.17940 for tilting rotors; 1.0 otherwise. Based on 51 aircraft, the average error of the<br />
blade equation is 7.9% (fig. 19-4). Based on 51 aircraft, the average error of the hub equation is 9.2%<br />
(fig. 19-5). For teetering and gimballed rotors, the flap frequency ν should be the coning frequency. The<br />
fairing/spinner and blade fold weights are:<br />
Wspin = χspin 7.386NrotorD 2 spin<br />
Wfold = χfold ffoldWblade<br />
The blade weight is for all blades of the rotors. If the weight is evaluated separately for each rotor, then<br />
Nrotor =1should be used in the equations. Typically ffold =0.04 for manual fold, and ffold =0.28 for<br />
automatic fold. Parameters are defined in table 19-3, including units as used in these equations.<br />
Table 19-3. Parameters for rotor weight.<br />
parameter definition units<br />
Nrotor number of rotors<br />
Nblade number of blades per rotor<br />
R rotor radius in hover ft<br />
c rotor mean geometric blade chord ft<br />
Vtip rotor hover tip velocity ft/sec<br />
νblade,νhub flap natural frequency (for weight estimate) per rev<br />
Dspin spinner diameter<br />
blade fold weight (fraction total blade weight)<br />
ft<br />
ffold<br />
For lift-offset rotors, the blade and hub weights can be calculated based on the methodology of<br />
reference 3. The blade and hub-hinge weights are:<br />
wblade = Nrotor 0.000041466 wR 3 /(2ht 2 .2R)<br />
whub = Nrotor<br />
<br />
0.17153 wRNblade<br />
+0.000010543(Wblade/Nrotor)V 2<br />
+0.081304 wR 2 <br />
2hL/t.2R<br />
tipt.2R/R<br />
Wblade = χbladewblade<br />
Whub = χhubwhub