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DO YOU KNOW YOUR PTANT?

The supercharged power plant of the modern tion, and shows how all factors work together airplane is indeed a complex machine. With to produce the manifold indicated on automatic devices such as constant speed pro- the instrument panel. pellers, electronic controls, and The first unit in the cycle is the . This for controlling fuel-air mixtures, removes dust and fine sand from the air enter- it is a far cry from the of 20 ing the power plant, preventing the rapid wear years ago. such grit would cause on moving engine parts. In this discussion of its operation, it is essen- A slight drop in pressure results from the pas- tial first to consider the power plant as a whole, sage of air through the filter, but rvhen the since when one factor in the intricate system turbo control is working the turbo compressor changes, other factors-even those apparently rpm is increased to cornpensate for the drop. remote-may also be afiected. For clarity's sake, At high altitudes, however, you should trrrn the discussion will deal chiefly with the elec- the filters off, or the turbine will reach over- tronic turbo-supercharger control, rather than speed at a lower altitude than normal. the early type with oil regulated control. Next is the turbo-driven compressor. The To gain a better understanding of the oper- amount of pressure boost it delivers depends ation of a supercharged engine, and thus help upon its rpm and upon inlet pressure. Four clear up the existing confusion about manifold factors afiect the rpm of this unit: Exhaust pres- pressure and its influence on engine perform- sure in the turbine nozzle box; exhaust gas ance, 1et us first consider the accompanying temperature; atmospheric pressure and temper- diagram. It shows the location of ,the various ature, and quantity of air flow through the parts of the power plant which afiect manifold compressor. pressure during the complete cycle of opera- Leaving the compressor, air passes through RESTRICTED t05 RESTRICTED

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a BB c, oa e=Eee9, g E (JEDe ==.-F9E 4E s-=2EEEE 9: = == r06 RESTRICTED RESTRICTED the . Since this is an integral part of Another function of the is to the induction system, a pressure drop occurs regulate the mixture of fuel and air, maintain- here whether the intercooler shutters are open ing the weight ratio constant in the normal or not. For full power conditions, this drop operating range. Manual mixture adjustment is amounts to approxirnately 1" Hg. provided for high and low power conditions. The regulator sensing uni.t, or Pressuretrol, Changing from automatic rich to automatic is connected to the induction system between Iean doesn't afiect manifold pressure appre- the intercooler and the carburetor. It reacts ciably, but excessive carburetor inlet pressure to the carburetor inlet pressure (CIP), or upper affects the mixture. Carburetors on B-24 air- deck pressure. This not the manifold pressure, planes are designed to maintain a constant is the pressure the pilot selects with the turbo fuel-air ratio for variable inlet up to boost selector (TBS), which operates through 31" Hg. Above this pressure the mixture be- the Pressuretrol to control the waste gate posi- comes lean; if carried too high, this causes deto- tion and produce the required CIP. (On the old nation and high -head temperatures. type oil regulated turbos, there is no Pressure- The next unit in the system is the internal trol, and the CIP has no efiect on waste gate blower. Since this blower is driven directly setting.) by the engine, any change in engine rpm causes Since the regulator reacts to the CIP, it is the blower speed to change. This causes a irnportant that the ducts and joints of the entire change in the boost added to the lower carbu- system be tight. Remember that altitude in- retor deck pressure to give the indicated mani- creases the pressure difierence between the fold pressure. inside and outside of the system; a leak that is At higher engine speeds with rvide open not apparent during ground operation or at , the boost from this blower is a large low altitude will cause a greater pressure loss part of the total manifold pressure, and a small at altitude. Leaks will cause excessive "droop" change in engine rpm, resulting from a sluggish and unstable power, and will make the turbo propeiler governor, will bring a noticeable overspeed control cut in below the nolmal alti- change in manifold pressure. (This effect is tude. common in low temperatures, which cause the The next unit in the system is the carburetor, oil in the dome to congeal and slow where the position of the throttle controls the the rate of change in prop pitch. You can cor- manifold pressure. When the throttle is at its rect this by working the prop governor back optimum position (ofiering minimum resistance and forth a few times to send u'arm engine to air flow), the rnanifold pressure will be at a oil through the dome.) maximum if other factors do not change. The If the engine rpm is reduced excessively, the optimum position of the throttle butterfly is turbine will have insufficient gases to operate not wide open, but several degrees from this on and a complete collapse of the cycle may point. Opening it beyond the optimurn position occur. This gives the impression of improper may cause an instability and loss of manifold turbo-supercharger regulation. When it occurs, pressure. If the open-throttle stops are set so the engine rpm should be increased. that the throttle cannot open to the optimum The next part of the system is the intake position, an excessive pressure drop will exist manifold, which obviously must be leak-proof across the carburetor. In order to obtain take- if you are to get stable pressures. The engine ofl power, the regulator would have to be re- itself comes next. Since manifold pressure calibrated to give a higher induction pressure. depends upon a uniform flow of exhaust gas to (The regulator should not be re-calibrated to drive the turbine, it follows that any flaw in offset incorrectly adjusted throttle stops, how- engine operation-faulty valve action, faulty ever.) This condition will exist at all altitudes ignition, or changes in rpm-rvill alter the and will cause the turbine to overspeed at a manifold pressure by causing fluctrrations in lower altitude. exhaust pressure. Ignition is a common cause

RESTRICTED 107 RESTRICTED of unstable manifold pressure at altitude, to relieve exhaust back pressure, and then because decreased atmospheric pressure leads closes it at a slower rate to establish the limit- to increased leakage throughout the electrical ing turbo speed. Since turbine speed, instead system. The must be in perfect of pressure, is controlled, a slight instability condition to ofiset this tendency at altitude. in manifold pressure will exist at higher The exhaust duct, turbine, and waste gate powers. The fluctuation warns you when the complete the supercharger systern proper. The overspeed control takes efiect. position of the waste gate controls the speed Note: Manifold pressure should be reduced of the turbine by determining the amount of slightly whenever the overspeed control goes exhaust back pressure and, consequently, the into operation. The device is designed to work amount of exhaust flow through the turbine when the turbine reaches maximum rated wheel. The TBS knob and the Pressuretrol, as speed plus 10/o. This overspeed rating should already explained, act upon the waste gate be limited to 5 minutes, as continued operation motor to control the position of the waste gate would greatly shorten the life of the turbine by reference to CIP. A further control of tur- wheel. Reduce the turbine rpm about 10% by bine speed is exercised by the overspeed con- reducing manifold pressure approximately 1.5" trol feature of the governor. Hg, and continue to reduce it by 1.5" for each 1000 feet you climb above that point. The parts of the regulating mechanism which The foregoing discussion is a general explan- can cause hunts in rnanifold pressure are the o ation of how your engine works. The material governor and the Pressuretrol. Improper func- which follows deals in greater detail with the evident all tioning of these units will be at individual parts of the power plant. altitudes whenever boost is being used. To prevent turbine speed from overshooting Tu rbo-superchorgers its limit during power changes at altitude, the The turbo- are installed behind overspeed control opens the waste gate rapidly the mount support of each engine, below the

r08 RESTRICTED RESTRICTED wing's lower surface. On early series B-24's, type B-2 turbos are used, while late B-24's have type B-22 turbos. The two types are al- most identical in appearance, but difier in their limitations. The B-22 has a higher maximum rpm, and therefore a higher critical altitude, than the B-2. At normal rated power-2550 rpm and 46" Hg.-the B-22 has a maximum wheel speed of 24,000 rpm, compared to 21,300 rpm for the B-2. At military power-2700 rpm and 49"- these speeds rise to 26,400 for the B-22 and 22,400 for the B-2, but use of this power is limited to 5 minutes. Because of the greater wheel speed, the B-22 turbo has a critical alti- Eledric Energy tude of 30,000 feet, as against 27,000 feet for the The source of all electric energy used by the B-2 turbo. turbo-supercharger control system is one of When you reach the critical altitude of the the airplane's 400-cycle i.nverters mounted type of turbo you are using (or when the over- under the flight deck, on the right side. AI- speed control takes efiect on the B-22 type, though 2 such inverters are installed in the producing fluctuations in manifold pressure), airplane, only one is used at a time. Either reduce manifold pressure 1.5" for every addi- inverter supplies the 115-volt, 400-cycle alter- tional 1000 feet you climb at maximum mani- nating current needed by the electronic con- fold pressure. If you are climbing at less than trol system. the rnaximum pressure, you can raise the crit- Inlercoolers ical altitude 1000 feet for each 1.5" that your manifold pressure is below the maximum. Heat from compression of the air by the turbo- superchargers Thus, if the critical altitude is 30,000 feet at 46", must be dissipated before it reaches the engine; it will be 32,000 feet at 43", etc. otherwise, the normal - buretor intake temperature Controls: The superchargers are regulated limits will be exceeded. This is accomplished either through the engine oil pressure system by or radiators in the intake or by electronic control. With the oil-regulated air duct between the turbo-supercharger and system, used on early B-24's, the pilot regu- the carburetor. Shut- ters on the intercoolers are provided to regulate lates the turbos by means of 4 levers on the left side of the pedestal. The levers control the operation of the waste gates on the 4 engines through the oil type regulators. The electronic control is used on all late B-24's and is replacing the oil-regulated type on most early aircraft. In this system, the TBS knob is the manual control unit. It is mounted on the pilot's pedestal in the space formerly occupied by the 4 turbo levers. The TBS unit contains 4 small calibrated potentiometers which require adjustments only to compensate for small difierences in engine or turbo per- formance. Once the calibrators are set, the pilot controls the turbo boost on all 4 engines simul- taneously by turning the control knob.

RESTRICTED r09 RESTRICTED the carburetor air temperature. The shutters Iimit. The other part, the accelerometer, antici- have 2 positions-{ull open and full closed. pates the pressure increase from turbo acceler- Extreme caution should be exercised when ation and provides a signal to start opening the using intercooler shutters, and carburetor air waste gate in time to prevent the overshooting and cylinder-head temperatures must be of manifold pressure. watched closely. The Amplifier The amplifier is an intermediate unit between the control units and the waste gate motor. It receives two kinds of signals from the other control units. One kind calls for rotation of the waste gate motor to close the gate; the other, for rotation to open it. After amplifying the sig- nal, the amplifier determines the dilection of movement called for and controls the power delivered to the waste gate motor accordingly. If the amplifier of any one of the 4 turbos fails, the waste gate remains fixed in the posi- tion it held when the amplifier went out. It is possible, however, to adjust all 4 turbos to any desired manifold pressure even if only one of the 4 amplifiers, or the spare, is working. To do so, it i.s necessary to disconnect the cannon plugs from the amplifiers (accessible from the

l. Wiper 3. Reference Bellows 2. Pofentiomeler 4. Operoting Bellows 5. Vent ond Droin

The Pressurelrol Control of the pressure in the induction system is accomplished automatically by the Pressure- trol. This unit measures electrically the pres- sure of the air supplied by the turbo-super- charger to the carburetor, and controls the automatic operation of the system to maintain whatever manifold pressure the pilot has se- lected, regardless of the changes in the atmos- pheric pressure caused by variations in the air- plane's altitude. It consists of a voltage-dividing potentiometer operated by a pair of bellows, connected to the induction system near the car- buretor inlet. The Turbo Governor The governor is a dual safety device driven by a flexible drive shaft which is geared to the turbo-supercharger. One part of the mechan- ism, called the overspeed control, prevents the turbo frorn exceeding its safe operating speed rlo RESTRICTED RESTRICTED

bomb bay). Then remove the dead amplifier for the desired position. This procedure can be used the turbo you wish to set up, and replace it in flight or, if necessary, to set up desired power with the good amplifier, reconnecting the can- for takeofi. non plug. (The pilot must be on the alert for The Wqste Gote Molor any turbo fluctuations, keeping his hand on the When the waste gate motor operates the waste throttle to control sudden changes, until the gate in response to the control signals, it also amplifier warms up.) From that point on, the operates a balancing potentiometer which pro- procedure is normal, except that when the duces a signal opposed to the original control turbo is properly set up, the cannon plug is signal. When the rotation of the motor is again disconnected, freezing the waste gate in enough to make the 2 signals exactly neutralize

. ,, I .;

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TURBO.SUPERCHARGER AND REGUTATOR SYSTEftIS

l. Exhoust Toil Pipe ll. Turbo-superchorger Ahernofe Air Intoke Duct 2. Turbo-superchorger Cooling Cop 12. Auxiliory Wing Fuel Tonk Monifold Connection Turbo-superchorger 3. Bucket Wheel 13. Alternore Air Intoke Filter Box 4. Air Ducf from Superchorger !o Intercooler 14. Woste Gqte Control Molor 5. Exhoust Wosle Gote 15. 6. Wosie Gote Confrol Linkoge Electric Coble 7. Exhoust Toil Pipe Outlel 16. Turbo Regulotor Governor 8. Intercooler Shutter Control linkoge 17. Turbo-superchorger Air Intoke Duct 9. Inlercooler Motor Conlrol Box I 8. Turbo-superchorger lO. Intercooler Motor 19. Oil Cooler

RESTRICTED tlt RESTRICTED each other, the power from the amplifier is cut ing turbo boost selector clockwise. off, and the waste gate motor stops. 7. Cruising-Use dial to select manifold pres- Operoting Inslructions sure. If manifold pressure cannot be lowered Electronic Turbo Control sufficiently with the knob, pull hack on the 1. Engage the Systern-After turning on the air- . Decrease rpm to desired value, and plane's battery switches, the main line switch, then, if necessary, re-set the manifold pressure and one inverter switch, allow 2 minutes for the with throttles and dial amplifier to warm up. The control system will If icing conditions prevail, close intercoolers then respond to the setting of the turbo boost and operate as close to full ,throttle as possible. selector. If has already formed (indicated by reduced 2. Before Starting Engines-Set turbo boost manifold pressure) open throttle and increase selector at "0." Turn on . power settings until manifold pressure returns Warnihg: Never turn inverter off while engines to normal. Watch cylinder-head temperatures are running, since the control system is depend- closely when intercooler shutters are closed. ent on the AC power for operation. 8. Emergency Power-Use only with Grade 3. Taxiing-Set dial at "0" unless turbo boost 100 fuel. Put mixture in "AUTO-RICH." In- is needed. crease rpm to maximum. Open throttles to the 4. Engine Run-up-Set propeller governors stops. Press dial stop release and turn dial for takeofi r'pm and check the manifold pres- clockwise to "10." sure on each engine separately by advancing Caution: Use only under extreme emergency throttle to full open position. Then turn dial of conditions. turbo boost selector to the desired position No-boost Ground Run-up ("8" with Grade 100). If the manifold pressure The check recommended in Item 4 of the fore- on any engitre fails to come up to within 1" of going procedures is an important step in de- the takeofi pressure with full rpm, turn dial to termining engine effi.ciency, and as such calls "0" and check the engine rpm and manifold for fuller explanation. In a normal ground run- pressure without turbo boost. This will show up, engine speed is increased by advancing the whether the 1ow manifold pressure is caused throttle, with the prop remaining fixed at min- by faulty engine operation or by insufficient imum pitch. Since prop pitch does not change, turbo boost. Also check DC voltage on the volt- engine rpm above 1200 increases directly with meter, with generators on. \ manifold pressure. At full throttle, maximum Note: If engine does not attain full takeoft rpm, the boost from the internal blower is a rpm, manifold pressure will be correspondingly major factor in manifold pressure. Any engine less. (A 100 rpm deficiency in engine speed will deficiency which reduces also re- produce 1% inches drop in manifold pressure.) duces rpm, and in turn causes manifold pres- 5. Takeoff-Turn turbo boost selector to de- sure to fall off and further decreases horse- sired position ("8" with Grade 100) and then power and rpm. The no-boost run-up, therefore, open the throttles. serves as a good indication of the condition of Note: Be sure generators are on and operat- the engine when the manifold pressure and rpm ing during and after takeoff; otherwise com- are compared to those of an engine known to plete electrical failure may result from low bat- be operating properly. In making the iompari- teries causing failure of electronic control. son, it is important to take atmospheric pres- 6. Climbing-After takeofi, turn knob coun- sure and wind direction and velocity into con- terclockwise until desired manifold pressure is sideration. Because of the change in prop load- reached. Decrease rpm to desired value. Re-set ing, a rise in wind velocity from zero to 25 mph manifold pressure with turbo boost selector if may alter engine speed by 50 rpm. In the range necessary. For climbing after cruisinq, increase of engine speeds above 1400 rpm, rprn may be rpm first; then advance throttles and increase changed by altering prop pitch, keeping the manifold pressure to the desired value by turn- throttle position fixed. 112 RESTRICTED RESTRICTED

Overspeeding Turbo-superchorger with throttle retarded, pull back the super- This occurs infrequently but usually on take- charger control and control power with throttle. off. An overspeeding turbo is evidenced by the Cqrburetor qnd Mixlure Controls manifold pressure quickly going sky-high. A turbo can overspeed during takeoff and then The R-1830-43 engine is equipped rvith the settle down immediately afterward and con- Bendix Stromberg injection carburetor. The tinue to operate normally. R-1830-65 engine has the Chandler-Evans Com- If you know a turbo is overspeeding during pany (Ceco) carburetor. Metering of the fuel is the first third of takeoff, it is best not to take off accomplished by air flow through the carbu- if you have room in which to stop. retor venturis. Four positions of the pilot's mix- ture control lever can be used in operating the Remedy With Electronic Control Bendix Stromberg carburetor: "IDLE CUT- Don't feather with an overspeeding turbo. Re- oFF," "AUTO-LEAN," "ALJTO-RICH," and duce manifold pressure with throttle. You ean't "FULL (EMERGENCY) RICH." With the dial back supercharger setting or you wiII lose Ceco carburetor, only the first three of these manifold pressure on all 4 engines. positions have any efiect; the "FULL RICH" With the electronic supercharger control, a position on the control quadrant does not work. runaway supercharger is usually directly trace- On all mixture control quadrants, however, the able to amplifier failure or insufficient electric "FULL RICH" position is safety-wired ofi from power. Amplifier tubes control the opening and the other three positions. An explanation of the closing of the waste gate, and if the tube that control positions, and their efiects, follows: controls opening of the waste gate is burned Automatic Rich-The usual operating posi- out, the supercharger may overspeed, There is tion for mixture control, "AUTO-RICH" main- a spare amplifier aboard and it can be changed tains the necessary fuel-air ratio for all flight as soon as you reach a safe altitude. conditions. At high power, the proportion of Caution: Reduee power on the affected en- fuel to air is relatively high, to suppress detona- gine when changing the amplifier, if circum- tion and assist in cooling. Between normal rated stances permit, and give it 2 minutes to warm and cruising powers the proportion of fuel is up. Then you can resume power. decreased, so that in the cruising range fuel Never shut the inverter ofi for any length of consumption is reduced to the minimum re- time without reduging power before bringing quired to prevent detonation and over-heating inverter on again. (Avoid turning inverter ofi and to provide good acceleration. unless in an emergency.) Automatic Lean-"AIJTO-LEAN" is an alter- nate operating position of the mixture control, Remedy Wirh Oil-Reguloted Control resulting in leaner fuel-air ratios than auto- On the oil-regulated type turbo, .overspeeding matic rich. During the favorable conditions of usually results from clogging of the legulator stabilized level flight or a cruising descent, balance lines or from congealed oil. The tend- automatic lean may be used in the cruising ency to overspeed will usually be evident when power range when fuel economy is of primary you are setting turbos during run-up. importance and when cooling is adequate. Don't Don't feather. You are getting porver from try to use intermediate settings beyond the the engine, and you can use it. For the first step, "AUTO-LEAN" position. You gain nothing by you have two choices. Either pull back the any such attempt at rnanual leaning of the supercharger control or reduce throttle to the mixture. desired manifold pressure. Reducing throttle is Full Rich-"FULL RICH" setting of the mix- better because if the supercharger settles down ture control renders inactive the altitude com- after takeofi, it is easier to re-set the throttle pensating device built into the carburetor to than the supercharger control. compensate for changes in the density of the If the tuibo wheel continues to oversneed air flowing through the venturis and keep the RESTRICTED r 13 RESTRICTED

fuel-air ratio constant. "FULL RICH." in real- ity, is merely a manually enriched mixture, and should only be used when the automatic mix- ture control unit gives evidence of faulty oper- ation. Despite its other name of ,,EMER- GENCY RICH," "FULL RICH" actually re- sults in a loss of power whenever it is used. Torquemeter tests show, for example, that at 8500 feet, with 35" manifold pressure, 2500 rpm, and "AUTO-RICH," an engine develops g35 Hp. With the same settings and "FULL RICH," the engine develops only ??5 HP-a loss of 160 Hp. Idle Cut-Ofr-Moving the mixture control past automatic lean to the end of its travel will stop all fuel flow, regardless of fuel pressure. "IDLE CUT-OFF" is intended for stopping the When air is pouring through the induction engine without the hazard of backfiring. system, sufficient temperature drop may cause precipitation Mixture strength is increased when operat- of moisture. If the temperature is low enough ing below the cruising power range. This en- in the system, the moisture will freeze and richment provides easier starting and the de- adhere to the closest surface. Forma- tion pendable acceleration needed in taxiing and of this ice anywhere in the induction sys_ the approach for a landing. Fuel metering in tem can block ofi the flow of air to the engine this power range is accomplished largely by and can cause almost instantaneous engine throttle opening. failure. The accelerating pump is operated by, and in Carburetor ice in the B-24 can occur during proportion to, the momentary changes in air otherwise ideal flying conditions. It can occur when pressure in the manifold entrance. The ac- it is snowing or sleeting. ft can occur any celerating pump is not connected with the throt- time carburetor air temperature is within the tle or throttle controls. Hence, when the engine icing range. Watch your carburetor air tem_ perature is not running, no fuel is pumped from the car_ when relative is high. buretor when the throttle is moved, no matter Know your induction system and tvhat hap_ pens how rapidly. You can not prime by pumping to the air pouring through it. Within B the throttle. hours' time your induction sysiem will use air weighing as much as the airplane. Corburefor lcing Detection of Carburetor fce-Icing can pro_ This is the most talked of and least under- gress almost to the point of engine failure be- stood type of icing. It is generally agreed that fore it is indicated on your instruments unless there is no such thing as a non-icing carburetor. you are alert. However, carburetor ice and the remedies {or 1. Know your carburetor air temperature. If it difier with each type of aircraft because of it drops down to 15.C when humidity is high the difference in carburetors. Inductic.rn-system ice can occur in the B-24. It is more likely to be refrigerated ice than atmospheric ice. Atmospheric ice can build up on any surface directly in the path of the intake air, such as +,ilTry= rcrNc the intercooler, carburetor butterfly valve, or the angle of the carburetor adapter (usually in the order named). It4 RESTRICTED RESTRICTED

take measures to bring it back up. Safe range heat in the air. This air is going to the carbu- is 15' to 35"C. Above 35oC there is danger of retor and would normally be too hot, so it detonation. passes through the intercooler. Whe.n inter- 2. Note any drop in manifold pressure. A 1ow cooler shutters are open, cool air, taken in carburetor air temperature, together with a through the air duct in the engine cowl, cools drop in manifold pressure, suggests carburetor the hot air pouring through the intercoolers. icing. (Do not mistake a drop in manifold pres- When you close the shutters, the intercooler sure caused by change in altitude for crarburetor has no cooling effect so that the blast of hot air ice.) from superchargers goes uncooled to the car- 3. If you have low carburetor air tempera- buretor, melts ice and very rapidly builds up ture, plus a sudden drop in manifold pressure, the carburetor air temperature. If this goes too plus a rough-running engine-then, brother, high, you get detonation and engine failure. you probably already have carburetor ice. Closing your intercooler shutters, obviously, not raise Prevenlive Meqsures will your carburetor air tenrperature unless turbos are operating. If you are flying at cruising power in c-onditions where there is danger of , close No Carburetor Air Temperature Gage: If your plane the intercooler shutters and operate as close to is not equipped with carburetor air full throttle aS possible. If ice has already temperature gages, you are short the most im- formed (its formation will be ipdicated by re- portant instruments for detecting carburetor duced manifold pressure), open the throttles ice and for observing the effects of intercooler and increase engine power settings until man- shutters. It becomes even more vital that you ifold pressure returns to normal. know relative humidity of the air through Caution: Check cylinder-head temperdture which you are flying. Avoid closing intercooler gages frequently whenever you are operating shutters unless you know there is danger of with the intercooler shutters closed. Excessive carburetor ice and then close them intermit- cylinder-head temperatures cause detonation. tently for only a few seconds at a tinre. Leave them open the instant you note a rise in cyl- Funclion of Intercooler Shutlers inder-head temperatures or a recovery of mani- When the turbo compresses air, it generates fold pressure.

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I RESTRICTED P(lITER SETTIlIG$

Grqde 9l Fuel-Specificotion ANF-26 OPERATION SETTING I,IIXTURES RPM MP TIIt'tE LIMIT BI,IEP HP Tokeoft Mox. Auto-rich 2700 42', 5 Minules 169 1060 Climb Mox. Auto-rich 2550 38', I Hour 160 950 Climb Desired Auto-rich 2550 35', Conlinuous 147 870 Cruise Auto-leon l65O-2lOOx30' Conlinuous Locol Cruise Suggested Aufo-leon 2000 30u Conlinuous l3t 610 *Moximum ond minimum rpm in Aulo-leon. Do nol exceed 3O" monifold pressure.

Grode IOO Fuel-Speclficction ANF-28 OPERATION SETTING tl,llxTuRES RPTt't MP TIME LIITAIT BTIEP HP Tokeoff Mox. Auto-rich 27OO 49" * SMinules 192 1200 Climb (Normol Roted Power) Mox. Auto-rich 2550 46" Conlinuous* 186 I too Climb Desired Auto-rich 2550 41' Cbnlinuous 167 990 2325 35" Conlinuous | 52 820 Cruise Mox. Auto-rich' cruise Mox. Auto-leon 2200 32u Conlinuous t40 715 Cruise Desired Auto-leqn 2OOO 30" Confinuoue | 3l 6ro *Cyf . heod lemp. nol lo exceed 232"C. For lemperolures of 232" lo 260o, lime limit is I hour.

DEFIlITTIONS OF RATI]IGS head temperatures do not exeded 232"C. Maximum Power and RPM for Cruising: This This is the maximum power Takeoff Rating: rating stipulates both the maximum power and speed permissible for takeoft and and engine maximum rpm permissible for continuous oper- to clear should be maintained only long enough ation with the mixture control in automatic obstructions. lean. The proper combination of rpm and man- maximum power Military Power: This is the ifold pressure for the particular horsepower, with less re- permitted for the military services load and altitude desired can be determined of the engine than for imme- gard for long life from the cruising control charts. diate tactical needs. Military rating is compa- In takeoff emergencies, you can get 1350 Hp rable to takeoff power with manifold pressures from your engines by using auto-rich, 2700 rpm, modified to suit altitude conditions, and may be manifold pressure. These settings give used for 5 minutes in any attitude of flight. and 56" Normal Rated Power: This is frequently re- you a BMEP (brake mean efiective pressure) power you ferred to as a normal maxirnum rating, or max- of 216. Use this emergency only if imum except takeofi power. It is the maximum have to, and then only for the shortest possible power at which an engine may be opelated con- time-never more than 5 minutes. Don't go into tinuously for emergency or high performance full (emergency) rich; you sacrifice power if operation in climb or level flight if cylinder- you do. rt6 RESTRICTED RESTRICTED $EOUE]IGE (lF P(IITER CHIlIGE$

On the other hand, too rich a rnixture inter- feres with the proper expansion and firing of the gases and results in overloading, torching, and loss of power.

Relotionship of Monifold Pressure ond RPM The constant-speed propeller does exactly what its name implies. The propeller governois function so that if propellers are set for a given rpm, governors automatically change the pitch o{ the propellers to keep them turning at the given rpm. Thus, if a propeller governor is set for 1900 rpm and manifold pressure is in- creased, the governors increase the pitch of propellers so they take a larger bite and con- There are ironclad rules regarding the sequence tinue to turn at 1900 rpm; this puts a larger for increasing or reducing power. Failure to load on the power.plant and builds up pressure follow the sequence can cause premature firing, in the cylinders. This is permissible within excessive pressures, overheating, detonation, specified limits, but as pressure increases heat and engine failure. Three inter-related ele- increases. An increase in the speed of propellers ments are involved in any power change, gives an outlet for the extra power being pro- namely: mixture, manifold pressure, and rpm. duced. Relofionship of Mixture ond Mqnifold Pressure Broke Meqn Effeclive Pressure "AUTO-LEAN," for example, automatically The brake mean efiective pressure (BMEP) ip reduces the proportion of fuel to air to. provide the average pressure within the cylinder of an efficient firing with minimum expenditure of engine during the power of the . fuel. However, as manifold pressllre is in- As the pressure within the cylinder is in- creased (increasing the pressure in the cyl- creased, more heat is developed because of the inders), there is a point beyond which the ex- energy of compression. If the pressure and cess pressure will cause hot, hard, and fast fir- temperature increase sufficiently, detonation ing, with detonation and overheating. If the occurs. fuel-air ratio is richer, the same manifold pres- The formula for determining BMEP for sure will produce slower, stronger firing, with 1830-43 or 65 P & W engines is: less heat. That's why richer mixtures must be BMEP:433 X BHP used at higher power settings. RPM tt7, RESTRICTED

STEPS F(|R I]IGREA$ITG

P(ITTER

3. Throttles. Pilot advances throttles as the rpm is in- creased. If more power than full throttle is re- quired, superchargers are advanced.

1. Mixture Controls. Copilot sets the mixture controls to "AUTO-- RICH" (if necessary) at pilot's signal. Reason: Maximum setting in "AUTO-LEAN" is 32" manifold pressure and 2200 rpm with Grade 100 fuel, and 30" and 2L00 rpm with Grade 91 fuel. It is obvious that if power is to be increased beyond these maximunrs the mixture should first be set in "AIITO-RICH." 4. Superchargers With electronic control, advance the TBS knob. With oil regulator, the supercharger con- trols may all be advanced together, but it is advisable to set them one at a time, starting with the dead-engine side if operating with a 2. Propellers. dead engine. Always use full throttle before Copilot increases rpm to desired setting. This applying supercharger boost. Reason: A par- should precede the manifold pressure increase tially closed throttle will create a back pres- to eliminate the danger of an excessive BMEP sure in the induction system resisting turbo (brake ) and resultant pressure. This causes a rise in carburetor air detonation. temperature with possible power loss and detonation-.

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$TEP$ F(lN REIIUCIlIG

P(IITER

before propellers in order to keep BMEP on the low side of safe limits and to prevent detonation.

3. Propellers. Copilot decreases rpm at command of pilot. This must follow throttles. A sufficiently low rpm permits mixtures to be brought to "AUTO- LEAN.'' l. Superchargers To reduce power, pilot first slowly retards supercharger controls-TBs or levers: slowly in order to prevent cracking of the turbo nozzle box by too rapid cooling, superchargers before throttles to prevent back pressure in induction system.

4. Mixture Controls. Copilot puts mixture controls in "AUTO- LEAN" if new power setting falls within limits of manifold pressure, rpm and cylinder-head 2. Throttles. temperatures. Wait until engines are cool be- Pilot retards throttles before reducing rpm. fore going into "AUTO-LEAN," because a hot Reason: Manifold pressures must be redueed engine increases the tendency to detonate.

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t RESTRICTED 14. Waiting Until Too Late to Correct for OAUSES (lF Carburetor Ice. 15. Improper Use of Inte4cooler Shutters Re- ElIGIlIE FAITURE sulting in Excessive and Deto- nation. Example: One pilot, at high altitude, thought he had an icing condition but failed to In considering engine failures, always remem- observe normal carburetor air temperature. He ber there are three things that make an engine closed the intercooler shutters, producing high run-fuel, oil, and ignition. Failure of any of carburetor air and cylinder-head temperatures, these three systems, plus structural failure, are followed by the failure of 3 engines. Never Iet the only things which can cause the loss of an carburetor air temperature get above 35oC, engine. especially when using Grade 91 fuel. Structural failure can be mechanical-the re- 16. Failure to Have Fuel Valve Selectors on sult of faulty construction or maintenance-but Tank-to-Engine for Take-off and Climb. One most of the time it is induced. Accident anal- pilot took ofi with all fuel valves on crossfeed yses show that pilot error far outruns mechan- with bomb bay transfer pump on, using gas ical failure in bringing about engine troubles. from bomb bay tanks only. After takeoff, co- Here are a few examples of stupid pilot errors pilot turned ofi the bomb bay transfer pump which induce engine failure; avoid them. switch, which is located on his instrurnent 1. Failure to Know Gas Consumption. Ex- panel, thinking it was a booster pump. Immedi- ample: A pilot flew 5lz hours on a practice ately 4 engines failed and the ship crashed. bombing mission in "AUTO-RICH" at a high L7. Improper Procedure With Overspeeding power setting. Airplane crashed and 5 men lost Turbo on Takeoff. Example: Pilot took ofi and their lives. experienced an overspeeding turbo, running 2. Failure to Reduce Manifold Pressure at manifold pressure beyond gage limits. He failed High Altitude. This can result in an overspeed- to reduce power and bring the turbo under con- ing turbo wheql disintegrating. One of the trol. The engine blew 5 cylinders and froze in buckets coming your way is just like a .50-ca1. high rpm. He managed to land, but unneces- bullet. sarily destroyed an engine. 3. Failure to Turn Booster Pumps On at High 18. Immediate Feathering of a Runaway Pro- Altitudes. peller When the Propeller Could Have Been 4. Increasing Power Without Changing Pro- Brought Under Control With Proper Proce- peller Setting. dure. Example: Pilot, during takeofi with a 5. Increasing Manifold Pressure Before RPM combat load, experienced a runaway propeller. Instead of After. Without trying to bring the propeller under 6. Failure to Use Auto-Rich in Power Set- control he feathered imrrlediately, He was un- tings Above Normal Cruise. able to maintain altitude and the ship crashed 7. Stiff-Arming Throttles. shortly after takeofi..Proper procedure would 8. Failure to Observe Engine Instruments have given l5 to 50% power on that engine. and to Control Excessive Temperatures. 9. Failure to Know the Fuel System for Par- ticular Airplane You Are Flying. 10. Waiting Too Long to Transfer Fuel. D E T0]t [T l01l 11. Taking Off in Auto-Lean. 12. Failure to Turn On Booster Pumps for Improper firing may be caused by a hot spot Takeofi, Causing Collapse of Fuel Lines or within the cylinder, an overheated sparkplug, Vapor Lock. eihaust valve, carbon d'eposit, etc. Once this 13. Failure to Observe Carburetor and Free gets started, it becomes progressively worse. Air Temperature IJnder fcing Conditions. The timing of the engines becomes uncontrolled

120 RESTRICTED RESTRICTED and roughness, and/or detonation, results. The high that the unburned portion of the charge is engine becomes overheated and loses power. ignited spontaneously, or detonated. Some of the factors over which you have con- The pressure of the unburned charge fluctu- trol, and which increase the tendency of the ates at a high frequency. These fluctuations lit- engine to detonate, are: High manifold pressure erally hammer the wall of the cylinder and with low engine speed; too lean a mixture; high cause the familiar knock. inlet temperatures; high cylinder-head temper- Even mild detonation will cause overheating, atures; and improper low-grade fuel' valve, piston, and cylinder-head burning, piston Under normal conditions, the fuel charge in scuffing, and and valve damage. a cylinder burns quite slowly. When detonation Severe detonation will cause engine failure in a occurs the first part of the charge within the short time. Complete engine failure can occur cylinder burns rapidly. This compresses the un- because of detonation during the time it takes burned part of the charge until the pressure you to make a takeofi run. The indications of and temperature within the cylinder rise so detonation are roughness and overheating.

SOIUIE EXATPTES OF FAUTTY OPERATIOlI

Mqnifold Cyl. Heod Oil Oil Fuel Corburefor Flight R.eoction Pressure Temp. Temp. Pressura Pressure Air Temps.

Broken Fuel Drop if Line Turbo on Ropid DroP Drop

Broken Oil Drop Line Rise Rise lo Zero

Breokcge of Moving Engine Possible Violent Violenl Ports Vibrotion Flucluqtion Unpredictoble Unpredictoble Voriqble Vqrioble

lgnition Rough R.unning Engine Flucfuqlion Trouble ond lntermittent Yow Flucfuolion if Turbo on DroP

Overheoling from Closed Proboble lnlercoolets Drop Rcpid Rise

Mixlure Too Torching Turbo or Block Drop R.ich Smoke Slight Drop Slight

Foilura of or Aulo-Mixlure Rise or Rise or Rise Feolure Rough R.unning Engine Fluctuofion Drop Drop Drop

Overspeeding Possible Turbo Overspeeding ViolenlRire Ropid R.ise R.ise

Runowoy RoPid Propeller Possible Vibrotion lncreose Drop Voriqble Vqricble

Corburetor Drop lce R.ough Running Engine Flucfuotion

Restricled Drop if Flucfuofion Fuel Flow Slighl Yow furbo on Drop

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