ENGINE MOUNT LOADS PROGRAM

Loads

The program ENGLOADS.BAS calculates the loads on the  engine 
mount  which the engine mount and its supporting  structure  must 
sustain.  FAR 23.361 requires loads resulting from engine  torque 
combined  with vertical inertia loads. For turbine  engines  this 
includes torque due to sudden stoppage. FAR 23.363 requires loads 
from  side  inertia.  FAR 23.371 requires  gyroscopic  loads  for 
turbine engines resulting from pitching and yawing velocities  in 
combination with propeller thrust and vertical inertia loads.

Equations

OMEGA  = RPM * 2 * 3.1416 / 60   Radians per Second

Where OMEGA is angular velocity

TORQUE = 550 * HP / (RPM * 2 * 3.1416 / 60 )   Foot Pounds 
THRUST = TORO*OMEGApr.op/V^^p^^g     Pounds

ALPHA = OMEGA / DT    Radians per Second per Second 
Where ALPHA is acceleration or deceleration 
DT is increment of time

TORO = I * ALPHA   Foot Pounds 
Where TORQ is reaction to engine angular acceleration

IProp = W / 32.174 * R2 / 3    Slug Feet4 
Where Iprop is ^s3"!181 of Propeller about Prop Shaft 
R is radius of Propeller

^otor = w / 32.1416 * R2 / 2    Slug Feet4 
Where Ipotor is Inertia of Turbine or Compressor Rotor

^aw = SUM ( I * OMEGAp^p ^ p^^ * OMEGAp^ ^ ) 
Where Myg^ is Yawing Moment due to Pitching Velocity

^Pitch ls sllnilar

Hand Calculation Examples

Gyroscopic Moment due to Yawing

Prop Dia = 101 In 
Turb Dia = 18 In 
Comp Dia = 18 In

Prop Wt - Hub Wt = 160-110 = 50 Lb 
Comp Wt = 35 Lb

253

FAR 23 LOADS

Turb Wt = 40 Lb

Ip    =W/g*R2/3=50/32.174*(50.5/12)2/3=9.174 Slug Ft4 
IComt> =W/g*R2/2=35/32.174*(9/12)2/2=.3060 Slug Ft4 
^urb =W/g*R'/2=40/32.174*(9/12)<::/2=.3500 Slug Ft4

OMEGA =RPM*2*3.1416/60

OMEGAp^-Q- =2200*2*3.1416/60=230.38 Rad/Sec 
OMEGAcomp =-33750*2*3.1416/60=-3534.3 Rad Sec 
OMEGA,i,m-b =33000*2*3.1416/60=3455.8 Rad/Sec

MOM-,t.ch =SUM(I*OMEGAs-,-*OMEGAy-,)

MOM-.-h=(9.174*230.38*2.5-.3060*3534.3*2.5+.3500*3455.8*2.5) 
=5604 FT LB

Note: A propeller on the nose of an airplane turning 
clockwise (as viewed from behind the propeller), if yawed to 
the left, will apply a pitch up moment to the engine mount.

Thrust for Turboprop

Max Torque = 1970 Ft Lb

Max RPM = 2200

Vcp = 60 Knots for Single Engine (Conservative for Multi-Eng)

VSF =60*1.15*88/60=101.2 Ft/Sec 
OMEGAp^op=2200*2*3.1416/60=230.38 Rad/Sec

THRUST =Torq*OMEGAp^op/Vgp=1970*230.38/101.2=4484.7 Lb

Torgue for Reciprocating Engine

Max HP = 285 
Max RPM = 2700

TORQ =550*HP/(RPM*2*3.1416/60)=550*285/(2700*2*3.1416/60) 
=554.388 Ft Lb

254

ENGINE MOUNT LOADS

3 REM----------------------------------------------------------------

4 REM          HEADING, COPYRIGHT, PRINTER MARGINS, MAIN PROGRAM

5 REM----------------------------------------------------------------

10 PRINT "ENGINE MOUNT LOADS --ENGLOADS.BAS, VERSION 1.0"

11 PRINT "(C) COPYRIGHT HAL C. MCMASTER 1988"

12 PRINT: INPUT "IS PRINTER READY ";QP$:QP$=LEFT$(QP$,1)

13 IF QP$0"Y" THEN 12

14 LPRINT CHR$(27)CHR$(78)XHR$(6):REM   SKIP OVER PERFORATIONS ON 
EPSON PRINTER

15 LPRINT CHR$(27)"1"CHR$(5):REM   SET LH MARGIN

20 LPRINT:LPRINT "ENGINE MOUNT LOADS"

32 LINE INPUT "ENTER ENGINE MANUFACTURER AND DESIGNATION SUCH AS ---

CONTINENTAL IO-520-BB   ";ENG$

34 LPRINT "FOR ";ENG$

36 LINE INPUT "ENTER PROP MFG & DESIGNATION SUCH AS ---HAM STD 1803

";PROP$ 
38 LPRINT PROP$

40 GOSUB 130: REM INPUT DATA 
50 GOSUB 400: REM 23.361(A)(1) ENG TORQ 
60 GOSUB 500: REM 23.361(A)(2) ENG TORQ 
80 GOSUB 700: REM 23.363 SIDE LOAD 
90 IF TYPE$="T" THEN GOSUB 600: REM 23.361(A)(3) ENG TORQ 
100 IF TYPE$="T" THEN GOSUB 800: REM   23.361(B)(1) SUDDEN STOPPAGE 
105 IF TYPE$="T" THEN GOSUB 1010: REM   23.371(B) GYROSCOPIC LOADS 
110 END

123 REM------------------- --------------------------------------.

124 REM         INPUT

125 REM------------------- --------------------------------------.

130 LPRINT:LPRINT "INPUT DATA":LPRINT

140 INPUT "ENTER LIMIT LOAD FACTOR, NZ ";LIMNZ

145 LPRINT "LIMIT LOAD FACTOR";TAB(30)LIMNZ

150 INPUT "ENTER ENGINE WEIGHT, LBS ";ENGWT

155 LPRINT "ENGINE WEIGHT, LBS";TAB(30)ENGWT

160 INPUT "ENTER ENGINE CENTER OF GRAVITY, X,Y,Z ";XENG,YENG,ZENG

165 LPRINT "ENGINE CG, X, Y, Z";TAB(30)XENG;", ";YENG;", ";ZENG

170 INPUT "ENTER PROPELLER WEIGHT, LBS ";PROPWT

175 LPRINT "PROPELLER WEIGHT, LBS";TAB(30)PROPWT

180 INPUT "ENTER PROPELLER DIAMETER, INCHES ";PROPDIA

185 LPRINT "PROPELLER DIAMETER, INCHES" ; TAB ( 30 )PROPDIA

190 INPUT "ENTER NUMBER OF PROPELLER BLADES ";NOBLADES

195 LPRINT "NUMBER OF PROPELLER BLADES";TAB(30)NOBLADES

200 INPUT "ENTER PROPELLER TAKE OFF RPM ";TORPM

205 LPRINT "PROPELLER TAKE OFF RPM";TAB(30)TORPM

206 INPUT "ENTER PROPELLER MAX CONT RPM ";CONTRPM

207 LPRINT "PROPELLER MAX CONT RPM";TAB(30)CONTRPM

210 INPUT "ENTER PROPELLER CENTER OF GRAVITY, X,Y,Z ";XPROP,YPROP,

ZPROP

215 LPRINT "PROPELLER CG, X, Y, Z";TAB(30)XPROP;", ";YPROP;", ";ZPROP

217 INPUT "ENTER TYPE OF ENGINE, R FOR RECIPROCATING OR T FOR 
TURBOPROP ";TYPE$:TYPE$=LEFT$(TYPE$,1)

218 LPRINT "ENGINE TYPE";

219 IF TYPE$="R" THEN LPRINT TAB(31)"RECIPROCAL"

220 IF TYPE$="R" THEN 250

225 IF TYPE$="T" THEN LPRINT TAB ( 31) "TURBOPROP" : GOTO 260

255

FAR 23 LOADS

250 INPUT "ENTER TAKE OFF HORSEPOWER " ;TOHP: LPRINT "TAKE OFF 
HORSEPOWER";TAB(30)TOHP

251 TOTORQ=TOHP*33000!/(2*3.1416*TORPM)

252 INPUT "ENTER MAX CONTINUOUS HP ";MAXCONTHP:LPRINT "MAX CONTINUOUS 
HP";TAB(30)MAXCONTHP

253 CONTTORQ=MAXCONTHP*33000!/(2*3. 1416*CONTRPM)

260 IF TYPE$="T" THEN INPUT "ENTER MAX ENGINE TORQUE, FT-LBS ";ENGTORQ

261 IF TYPE$="T" THEN INPUT "ENTER CRUISE ENGINE TORQUE, FT-LBS ";

CRUZTORQ

270 IF TYPE$="T" THEN LPRINT "MAX ENGINE TORQUE, FT-LBS";

TAB(30)ENGTORQ

280 IF TYPE$="R" THEN LPRINT "TAKE OFF TORQUE, FT-LBS";TAB(30)TOTORQ

325 IF TYPE$="T" THEN FACTOR=1.25

330 IF TYPE$="R" THEN PRINT "HOW MANY CYLINDERS?":INPUT CYL

335 IF TYPE$="R" AND CYL=>5 THEN FACTOR=1.33

340 IF TYPE$="R" AND CYL=4 THEN FACTOR=2

345 IF TYPE$="R" AND CYL =3 THEN FACTOR=3

350 IF TYPE$="R" AND CYL=2 THEN FACTOR=4

355 IF TYPE$="R" AND CYL<2 THEN 330

390 RETURN

393 REM-------------------- ------------------------------------------

394 REM TAKEOFF TORQ, 75% LIM VERT LOAD FACTOR COND A, FAR 23.361 (A) (1)

395 REM---------------------------------------------------

400 N75=.75*LIMNZ

405 PPWT=PROPWT+ENGWT

410 XPP=(PROPWT*XPROP+ENGWT*XENG)/PPWT XPP=INT(XPP*1000)/1000

415 YPP=(PROPWT*YPROP+ENGWT*YENG)/PPWT YPP=INT(YPP*1000 )/1000

416 ZPP=(PROPWT*ZPROP+ENGWT*ZENG)/PPWT ZPP=INT(ZPP*1000)/1000 
420 V1=N75*PPWT

425 IF TYPE$="R" THEN T1=TOTORQ

426 IF TYPE$="T" THEN T1=ENGTORQ

430 LPRINT:LPRINT "LIMIT TAKEOFF TORQUE WITH 75% LIMIT MANEUVER 
VERTICAL LOAD FACTOR"

431 LPRINT TAB(5)"FAR";TAB(31)"23.361(A)(1)"

432 LPRINT TAB(5)"VERTICAL LOAD FACTOR";TAB(30)N75 
435 LPRINT TAB(5)"VERTICAL DOWN LOAD, LBS";TAB(30)V1 
440 LPRINT TAB(5)"ENG MOUNT TORQUE, FT-LBS";TAB(30)-Tl 
445 LPRINT TAB(5)"APPLIED AT X , Y, Z";TAB(30)XPP;", ";YPP;", ";ZPP 
450 RETURN

493 REM------------------------------------------------------------

494 REM MAX CONTINUOUS TORQ X FACTOR & 100% LIM VERT LOAD FACTOR CND A 
FAR 23.361(A)(2)

495 REM-- --------------------------------------------------

500 N100=LIMNZ 
505 V2=N100*PPWT

510 IF TYPE$="T" THEN T2=FACTOR*CRUZTORQ 
520 IF TYPE$="R" THEN T2=FACTOR*CONTTORQ

530 LPRINT:LPRINT "FACTOR TIMES MAX CONT TORQUE WITH 100% LIMIT 
MANEUVER VERTICAL LOAD FACTOR"

531 LPRINT TAB(5)"FAR";TAB(31)"23.361(A)(2)"

532 LPRINT TAB(5)"VERTICAL LOAD FACTOR";TAB(30)N100

535 LPRINT TAB(5)"VERTICAL DOWN LOAD, LBS";TAB(30)V2

536 LPRINT TAB(5)"AT X, Y, Z";TAB(30)XPP; " , ";YPP;", " ; ZPP 
538 LPRINT TAB(5)"TORQUE FACTOR";TAB(30)FACTOR

256

 ENGINE MOUNT LOADS

539 IF TYPE$="R" THEN LPRINT TAB(5)"MAX CONT TORQUE";TAB(30)CONTTORQ

540 IF TYPE$="T" THEN LPRINT TAB(5)"MAX CONT TORQUE"; TAB(30)CRUZTORQ

541 LPRINT TAB(5)"ENG MOUNT TORQUE, FT-LBS";TAB(30)-T2

545 LPRINT TAB(5)"APPLIED AT X,Y,Z";TAB(30)XPP;", ";YPP;", ";ZPP

550 RETURN

593 REM---------------------------------------------------------------

594 REM   TURBOPROP PROPELLER CONTROL MALFUNCTION, FAR 23.361(A)(3)

595 REM-----------------------------------------------------

600 NZTP=1

610 TTP=1.6*ENGTORQ

620 VTP=NZTP*PPWT

630 LPRINT:LPRINT "TURBOPROP PROPELLER CONTROL MALFUNCTION"

631 LPRINT TAB(5)"FAR";TAB(31)"23.361(A)(3)" 
635 LPRINT TAB(5)"VERTICAL LOAD FACTOR";TAB(31)"1" 
640 LPRINT TAB(5)"VERTICAL DOWN LOAD, LBS";TAB(30)VTP 
650 LPRINT TAB(5)"ENG MOUNT TORQUE, FT-LBS";TAB(30)-TTP 
660 RETURN

693 REM-----------------------------------------------

694 REM          SIDE LOAD, FAR 23.363

695 REM------------------------------------------------------------

700 NY=LIMNZ/3

710 IF NY<1.33 THEN NY=1.33

715 IF TYPE$="R" THEN CONDK=3 ELSE CONDK=4

720 LPRINT:LPRINT "SIDE LOAD INDEPENDENT OF OTHER FLIGHT LOADS"

721 LPRINT TAB(5)"FAR";TAB(31)"23.363(A)&(B)"

725 S3=NY*PPWT

726 LPRINT TAB(5)"VERTICAL LOAD FACTOR";TAB(31)"0"

727 LPRINT TAB(5)"SIDE LOAD FACTOR";TAB(30)NY 
730 LPRINT TAB(5)"SIDE LOAD, LBS";TAB(30)S3 
735 LPRINT TAB(5)"APPLIED AT X,Y,Z";TAB(30)XPP;", ";YPP;", ";ZPP 
740 RETURN

793 REM--------------- ------------------------------------------

794 REM    TORQUE FOR SUDDEN ENGINE STOPPAGE, FAR 23.361(B)(1)

795 REM-------------------------------------------

800 LPRINT:LPRINT "INPUT DATA --- TURBOPROPS

803 INPUT "ENTER PROPELLER HUB WEIGHT";HUBWT

805 LPRINT TAB(5)"PROPELLER HUB WEIGHT";TAB(30)HUBWT; " POUNDS"

810 INPUT "ENTER COMPRESSOR DIAMETER, WEIGHT, MAX RPM";COMPDIA,COMPWT,

COMPRPM

820 LPRINT TAB(5)"COMPRESSOR DIAMETER";TAB(30)COMPDIA;" INCHES"

821 LPRINT TAB(5)"COMPRESSOR WEIGHT";TAB(30)COMPWT;" POUNDS"

822 LPRINT TAB(5)"COMPRESSOR RPM";TAB(30)COMPRPM

830 INPUT "ENTER TURBINE DIAMETER, WEIGHT, MAX RPM" ;TURBDIA,TURBWT, 
TURBRPM

831 LPRINT TAB(5)"TURBINE DIAMETER";TAB(30)TURBDIA;" INCHES"

832 LPRINT TAB(5)"TURBINE WEIGHT";TAB(30)TURBWT;" POUNDS"

833 LPRINT TAB(5)"TURBINE MAX RPM";TAB(30)TURBRPM

834 PRINT "ENTER TIME IN SECONDS TO STOP DUE TO SUDDEN STOPPAGE."

835 INPUT "FAA USUALLY ACCEPTS .3 SECOND.";DT

840 LPRINT TAB(5)"NOTE CLOCKWISE FROM PILOTS VIEW IS POSITIVE"

845 TOTALBLADEWT=PROPWT-HUBWT

850 IPROP=TOTALBLADEWT/32.174*(PROPDIA/2/12)>2/3:IPROP=INT(IPROP*1000)

/1000

860 ICOMP= . 5*COMPWT/32 .174*(COMPDIA/2/12 ) ~2: ICOMP=INT( ICOMP*1000 ) /1000

257

FAR 23 LOADS

870 ITURB=.5*TURBWT/32.174*(TURBDIA/2/12)-2:ITURB=INT(ITURB*1000)/1000

890 OMEGAPROP=TORPM*2*3.1416/60:REM RAD/SEC

892 OMEGACOMP=COMPRPM*2*3.1416/60

894 OMEGATURB=TURBRPM*2*3.1416/60

900 DT=.3

910 ALPHAPROP=OMEGAPROP/DT

912 ALPHACOMP=OMEGACOMP/DT

914 ALPHATURB=OMEGATURB/DT

920 TORQPROP=IPROP*ALPHAPROP

922 TORQCOMP=ICOMP*ALPHACOMP

924 TORQTURB=ITURB*ALPHATURB

926 TORQSUDSTOP=TORQPROP+TORQCOMP+TORQTURB

930 LPRINT:LPRINT "TORQUE FOR SUDDEN STOPPAGE DUE TO MALFUNCTION OR"

931 LPRINT "STRUCTURAL FAILURE (SUCH AS COMPRESSOR JAMMING)"

932 LPRINT TAB(5)"FAR";TAB(31)"23.361(B)(1) "

940 LPRINT TAB(5)"IXX PROPELLER";TAB(30)I PROP;" SLUG-FT~2"

950 LPRINT TAB(5)"IXX COMPRESSOR";TAB(30)ICOMP;" SLUG-FT~2"

960 LPRINT TAB(5)"IXX TURBINE";TAB(30)ITURB;" SLUG-FT~2"

965 LPRINT TAB(5)"TIME TO STOP";TAB(30)DT;" SECONDS"

980 LPRINT TAB(5)"ENG MOUNT TORQUE";TAB(30)INT(-TORQSUDSTOP ) ; " FOOT

POUNDS"

990 LPRINT TAB(5)"CLOCKWISE FROM PILOTS VIEW IS POSITIVE" 
1000 RETURN

1003 REM------------------------------------------------------------

1004 REM     GYROSCOPIC LOADS ON ENGINE MOUNT AT MAX CONTINUOUS RPM

1005 REM---------------------------------------------------------

1010 LPRINT:LPRINT "GYROSCOPIC LOADS ON ENGINE MOUNT AT MAX CONTINOUS

ENGINE RPM"

1020 TPITCH=IPROP*OMEGAPROP+ICOMP*OMEGACOMP+ITURB*OMEGATURB 
1030 TYAW=2.5*TPITCH 
1040 VSF=60*1.15*88/60 :REM  MIN STALL SPEED REQUIRED FOR SINGLE ENG,

CONSERVATIVE FOR TWIN 
1050 THRUST=ENGTORQ*OMEGAPROP/VSF 
1060 VERTLD2.5=2.5*PPWT 
1070 LPRINT TAB(5)"Myy DUE TO 2.5 R/S YAW";TAB(31)"+ OR - ";TYAW;

" FOOT POUNDS" 
1080 LPRINT TAB(5)"Mzz DUE TO 1 R/S PITCH";TAB(31)"+ OR - ";TPITCH;"

FOOT POUNDS"

1090 LPRINT TAB(5)"VERTICAL 2.5G LOAD";TAB(30)VERTLD2.5;" POUNDS"

1091 LPRINT TAB(5)"AT X,Y,Z";TAB(30)XPP;", ";YPP;", ";ZPP

1100 LPRINT TAB(5)"MAX CONTIUOUS THRUST";TAB(30)THRUST;" POUNDS"

1101 LPRINT TAB(5)"AT X,Y,Z";TAB(30)XPROP;", ";YPROP;", ";ZPROP

1110 LPRINT TAB(5)"FAR 23.371(B) REQUIRES ALL COMBINATIONS OF THESE 4

LOADS." 
1120 RETURN

258

