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Wx I 1 9th Part of' No. AkK/83/1-

MINISTRY OF SUPPLY

AEROPLANE AND ARMAMENT

EXPERIMENTAL ESTABLISHMENT

BOSCQMDE *DOWN'~

HASTflP0S 0.ri. I.7

QjEMULFS 106) U 4

RI-flE COOMNO^ TETss AT 8,, 00 LB. -'vT fim:' S000IN' F.0NS, AD ExTER1T.&L STO0RES I - W

z ~

z <U

C; -E 0 0I

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should forward It, together with his name and address, in a closed envelope to :

THE SECRETARY, MINISTRY OF SUPPLY, ~ ~ CI.T

Letter postage need not be prepeid : other postage will be refundsid.

All persns are hereby warned that the unauthorised retention or destruction of this document is an offence againstthe Ofk ficteret Acts, 1911-1939.

AIR ATTACH E, LONDON. 05(A08 t3515732.25521.&&sc.'4AAEE FORM 1. 05(A0)

9th Part of Report No. AAED/843/1.

AEROPLANE AND ARPIMF2AT EXPERI TAL EST1BLI ThNT ,BOSCOAIE MIN 7._.

Hastings C. 1.c. 2. 7D. 476(Hercules 106)

En,-(ine cooling tests at 80,000 lb. with and vithoutcooling fans, and external stores

A. & A.E.B. Ref.: AAIEE/5707,j/10.Period of Tests June, 1953.

Progress of issue of Report

Report No. TitleiI

4th Part of MM/83/1. V0D.475 Brief handling trials.

5th - do - WD. 475 Compass assessment.6th - do - ;7D.476 Take-off performance.7th - do - WD. 476 Noise level measurements.

8th - do - 17D.476 Investigation of air speeds duringtake-off and climb away.

Summary

The results of the engine cooling tests on Y/D.476, after making allowancefor such factors as the lower performance obtained with an external load ofhigher drag than that carried on test and for a less severe engine-operatingcondition on the climb, indicate that the cylinder temperature limitations willbe exceeded as follows with the cooling fans removed and under tropical summerstandard conditions: -

(i, Take-off 1500.(ii Climb 150.

(iii) Level flight at 8,000 feet 150C.(iv) Level flight at 1 ,000 feot, at a dropping t

speed of 115 knots, I.A.S. 30PC.

With the cooling fans fitted, (iv) is the only case likely to give riseto the limitations being materially exceeded.

On the assumption that the conditions of manoeuvre and powier settingsrelevant to the above, are representative of those used by Transport Commandin their operation of Hastings aircraft carrying extcrnal stores, withoutcooling fans, then it is reasonable to expect that similar levels of cylindertemperature are realised in Service. In fact, they may be materially higher.by reason of, - (a) the indications of cylinder temperatures displayed by the

standard pyrometers to the aircrew being much lower than those measured on thesame cylinder by test pyrometers, and (b) by the location of the standardpyrometers on cylinder No. 14 which is not the hottest in all instances,resulting possibly in the cowil gills being used in the shut position, when, infact, they should be open for increased cooling.

The foregoing does not take into account such circumstances as assymetricpowered flight folloving an engine failure on take-off and the practising ofovershoots with simulated engine failure. Either of theso would tend to resultin a material increase in cylinder temperature at take-off power setting.

/Since it....

-2-

Since it optiears that there has been no undue increase in the rate ofengine or relevant component failure during Transport Command's operation ofHastings aircraft in tropical climates with cooling fans removed, it is sugges-ted that the current cylinder tcrjorature limitations for the Hercules 106 canbe materially exceeded irith safety.

The potential dangers arising from the ral-functioning of the standard jsingle point pyrometers, combined with the fact that the cylindcr on which it

is located is not always the hottest, warrant consideration being given to thedeletion of the equipment in its present form.

The frequency vwith which mechanical failures of the cooling fan installa-tion has occurred on Hastings aircraft operated by Transport Oomm., suggests

that their retention may introduce a hazard greater than that due to the increase

of cylinder temperature arising fron their removal.

An investigation is proceeding into the reasons for the mal-functioning

of the standard single point pyrometer equipment.

This report is issued with the authority of k

Air Commodore,Commanding, A. & A. E. E.

/Introduction....

-- i

3-

1. Introduction

The high rate of failure of propeller driven engine cooling fans onHastings aircraft, has necessitated the removal of that cooling aid from 10-those aircraft operated by Transport Command. in consequence, the Air Ministryrequested M. of S. to give consideration to the follwiing:-

(a) technical clearance for world wide operation without the fans

fitted, or failing this

(b) the development and production of cooling fans having a reasonabledegree of mechanical reliability.

This request resulted in a number of meetings between the A.M., M. of S.,Bristols and A. & L.E.E. It was not possible to reconcile a number of view-points put forward during these discussions. In particular, the cylinder tem-peratures observed by Transport Command during operation in the Middle Fast ofHastings aircraft without cooling fans differed from those to be expected whenassessed on the basis of controlled engine cooling tests made in the tropics ona Hastings powered with Hercules 101 engines (with fans fitted), corrected forthe estimated effect of the change to Hercules 106 engines without cooling fans.In consequence it was reconmended that A. & A.E.E., with the assistance ofBristols, should conduct tropical engine cooling tests on a representativeHastings 2 aircraft, in the most adverse operational configuration of externalload.

Subsequent to the allotment of Hastings C. )&k.2.1D.476 for the trials,instructions were received not to proceed with the tropical tests pendingfurther information from the Air Ministry. Cooling trials were however, madeat A. & A.E.E., and the results of these tests form the subject of this report.

2. Description of aircraft relevant to tests

2.1. Gcncral. The aircraft is a standard Hastings C. 14ik. 2 aircraft,powiered with Hercules 106 engines, driving do Havilland 4-bladed hydromaticmetal propellers of 13 ft. diameter (Type D. 100/446/1. )

2.2. Enr~inc particulars. Production Hercules 106 enginesm were installedas follows: -

P.O. No. 137469 P.I. No. 137485

S.O. No. 137477 S.I. No. 137468

Fuel injectors, Hobson R.A.E. type BI/-. 5/3 were fitted to each engine.

Normal and weak mixture bleed filter screens were incorporated as a safe-guard against possible ingress of foreign matter. These filter screens do notaffect the flow characteristics of the injectors. I. standard ground tuningcheck was made ard all engines were within proscribed limits (see Fig. I).

The engine and propeller installations, in terms of the relevant aspectsof cylinder cooling, were to the current modification standard. The coolingfans (Type DMFI/1) were removed from Nos. 1, 2 and 4 propellers for the compara-tive tests referred to later. The fan was retained on No. 3 propeller throughoutthe tests to provide an undisturbed datum. The spinner back plates and spinnerswere in situ throughout all the trials.

/The....

N The relevant differences between the Hercules 106 and 101 engines are:-

(a) Take-off and o,)orational necessity boost is 81 lb/sq.in. for the 101,compared with 10 lb. q.in. for the 106.

(b) The 101 engine was tuned to the prescribed limits (common to bothseries) with an open exhaust, whereas the 106 engine was tuned tothese limits with the correct exhaust system fitted.

At the respective take-off power rating the specific fuel consumsption ofthe 101 engine with the correct exhaust system, is estimated to be 0.039 B/BIP/greater than that of the 106 engine with a similar exhaust system.

The air intake system was standard, allowing selection of rammed coldair, ramned clean air, or warm air.

_____The engine limitations declared for the Hercules 106 engine in Eng.R.L, 1(b)certificate ref. 7/Eng/3894 dated 7.12.51, are:-

Power condition R.P.M. Boost Cyl, Engine in oill b A ; a a . " t em . 'C

Take-off and operational necessity 2800 + 0 310 1 0

(5 mn. limit)Intermediate and max. emergency cruise 2400 +6 300 90Max. continuous 2400 +6 300 80Max. continuous with weak mixture 2400 +2- 300 80

2.3. Oil coolers. lawrence coolers to Drg. XHL.1 31 Issue 3, fitted toNos. 1, 2 and 3 engines; Serck cooler to Drg. No. .S.11440 Issue 4, fitted toNo. 4 engine.

2.4. Test instruments

(a) Cylinder head temperatures were measured at all front row positionsof each of the four engines, and at all rear row positions on No. 2 engine only.Elliott type gauges with ice-cold junctions were used throughout. No. 14 cylin-der temperature gauges were located at the flight engineer's station but allothers were mounted in an automatic observer. For certain tests, the standardsingle point3 pyrometers were connected to No. 14 cylinder of each engine

(b) Air temperature was measured on a balanced bridge type thermometer.

(c) Kent displacement type flowmeters were fitted to all engines, theimpulses from these being receivea by standard gallons gone counters, flashinglights, and direct reading indicators, the latter located in the automaticobserver.

(d) The standard niloth and flight engineer's instrunents (previouslycalibrated) were used for all test work, but No. 2 engine r.p.m. and boost,together with an altiLcter, A.S.I. and clock were dulicated-ihn the automaticobserver.

2.5. Loading. All tests ';cro made frow a tecc-off weight of 80,000 lb.With the exception of tests mentioned in the succceding paragraph, no externalload was carried.

The tests with extornal load were, for convenience, effected with 20supply containers C1 15k. 3 carried on racks under the fuselage and inboardwing section. This configuration was the nearest practicable approximation tothe worst drag case of the Hastings aircraft.

3. Scope of tests

All tests were made in l. Supercharger gear.

Flight tuning checks at take-off, intermediate and nax. continuous weakmixture power settings were made before conmiencing the cooling tests, and wererepeated towards the end of these tests.

The cooling tests covered ground cooling, take-off and climb at take-offpower for 5 r.ins, followed by climb at intermediate power to 8,000 feet. Testsin level flight at maximum weak mixture pover wore then made at 8,000 feet,followed by a shallow descent to approx. i ,000 feet, at which height a droppingrun was simulated. Repeat tests were made as indicated in the following table.

/Table....

Thermocouple:- Storc Ref.: 103542. Bristol Part. No. 139037.

- a

5

No, of Oontaina 'ooling Cowl-Condition tests on or fans o gill

____made. off. or oft settin_

Ground cooling for 10 mins. at 1400 r.p.m. 2 Off On Full open2 Off Off FIull open

Taake-off and climb at take-off power for5 eins, at 125 knots I.L.S. 4 Off On Full open

2 Off Off Full open1 On Off ull open

Climbs at intermediate power from end of 2 Off On Full opentake-off pvor, to 8,000 ft. at 130 knots 2 Off Off Full openI.A.S. I On Off Full open

Level flight at 3,000 ft. at max. contin- 2 Off On Shutuous power, weak mixture. 2 Off Off Shut

1 On Off (4- openon 2,3,

Full 70c. .. .. .. . . .... (on 1.)

Dropping run at 1,000 ft.,at 2400 r.p.m. I On Off 1 open onat 115 knots I..S. 1 and 2.

Shut on 3• and 4.

Fan on No. 3 engine for all tests.

During the 7round cooling tests, recordings were taken each 3 minutes.During take-off tests, recordings were taken each 10-15 seconds until I ,000 ft.altitude was reached. During continuation of climb at take-off power record-ings were taken at 500 ft. intervals, then at 1 ,000 ft. intervals afterthrottling back to intermeiate power. Recordings in level flight were takenat the end of 10 minutes, by which time the cylinder temperatures werestabilised.

4. Results of tests

4.1. General. The cylinder temperatures have been corrected to theI.C.A.N. standard of air temperature. Unity response of cylinder temperatureto air teingerature has been assumed in making that correction. The validityof that assumption, within the probable limits of the true value of the correc-tion factor, is not important in terms of either the standard to which theresults are corrected, or the comparisons made between different conditions;this is because the ambient air temperature on test was at no time more than300 below or above the I.C.L.1, standard.

All results quoted for a given condition of operation (c.g. power set-ting, configuration) are on the basis of mean values. Repeatability was normw-.lywithin the order of 50C or less but in some cases as much as 100C was encoun-tered; this excludes conditions of an essentially transient nature such as th,opening-up period during take-off.

Cylinder temperatures arc quoted to the nearest 50C in the succeedingparagraphs.

4.2. Tuning characteristics. These results are plotted in Figure 1and compared with the nominal fuel flow limits.

4.3. Ground cooling. The maximum cylinder head temperatures obtained.,with cooling fans, at 1400 r.p.m. Yrith propellers on the fine pitch stops,using clean air and 'H' gear with the gills fully open, were well within the

/relevant....

K

6

relevant limitations of 30000 (maximum continuous) and 23000 (recommendedmaximum before commencing take-off) with cooling fans fitted. Without thecooling fans, changes of temperature distribution pccurred, with attendantincreases in the maximum cylinder head temperatures which, however, werestill well within the aforementioned limitations. Polar diagrams showing 2

the temperature distribution at these conditions are given in Fig. 2.

4.4. Take-off and climbs The results are as follows:-

(i) Talce-off and initial climb. Figs. 3A to 3D show curves of thehighest cylinder temperature on each engine against time, zero time beingthat at which the aircraft brakes were released. With one exception, noparticular attempts were made to obtain specific cylinder temperaturesbefore starting the take-off, ard any differences in starting temperaturebetween various tests wore reflected to a less extent on attaining safetyspeed (125 knots I.A.S.) at about I min. after release of brakes. Within2 mins. of commencing the take-off, those effects wore no longer evident,the engines by this time having settled down to stabilised conditions,under which, alti-tude was the only variable affecting cylinder temperatures.

These curves also show the effect of removing the cooling fans fromNos. 1, 2 and 4 engines in terms of the hottest cylinder in that configura-tion. The maximum cylinder head tenmpratures at the take-off speed weresane 150 to 2000 greater with the fans removed, but thereafter the diffe-rence bocame progressively less. During the tests in which 20 containerswere fitted externa.lly, the time to attain safety bpod increased by about5 to 10 sees. but this increase had no significant effect on the maximumcylinder head temperatures, regardless of whether the cooling fans werefitted or not.

Polar di,-rans showing the cylinder temperature distribution of eachengine at a point approxirzmting to the stage at which the aircraft wasclimbed away at the safety speed of 125 knots t.A.S. are given in Fig. 4,the effect of removing the cooling fans is also illustrated in that Figure.

(ii) Sustained Climb. Fig. 5 shows curves of the highest cylindertemperatures on each engine against height, i.e. from a point approximatingto the termination of Figs. 3A to 3D, to the end of the 5 minute periodat take-off power, and subsequently to 8,000 ft. at intermediate power.

Due to differences in height at which the engines were throttled backto intermediate power, stabilised cylinder temperatures are only shownbetween 7,000 and 8,000 ft.

Cylinder teiroratures increased with height while at take-off power.At 4,500 ft. the higher altitudes common to all tests before throttlingback to intermediate power, the highest cylinder temperature reached therelevant limitation of 3100C on Nos. I and 4 engines with cooling fan on,and exceeded the limitation by 100C with fan off on Nos. 1, 2 and 4 engines.

The maximum cylinder temperature at intermediate power in the stabilisedheight range, 7,000 - 8,000 ft. ; were within the limitation of 300°0 in allinstances.

Figs. 6 and 7 show polar diagrams of the cylinder temperature distribu-tion on each engine at 4,500 ft. (take-off power) and at 8,000 ft. (interne-diate power) respectively. The diagrams also show the effect of removing thecooling fans from Nos. 1, 2 and 4 installations, in terms of cylinder tempora-ture distribution and highest cylinder temperatures.

The carriage of the 20 external containers did not significantly effectthe cylinder temperatures.

4.5. Level flipht at max. continuous nowor, weak mixture, at 8,000 feet.Polar diagrams" for this condition are shown in Fig. 8. Removing the coolingfans caused higher cylinder head temperatures but those were well withinlimits with the aircraft clean and cooling gills closed.

/Figure 9.....

KL...

-7-

Figure 9 shows polar diagrams of cylinder temperaturos with the fans of"nuribers 1, 2 and 4 installations, and the 20 cannistors fitted externally.The increase in temperature of the hottest cylinder due to the largo loss ofspeed experienced with the containers fitted, was estimited theoretically tobe about 25 - 30°C. The tests tendod to confirm this estimate, and varyingamounts of gill opening were necessary to keep the maximum cylinder headtemperatures within the limitation of 300C.

4.6. Level flight at 2400 r.p.m. P t 1,000 feet at 115 knots I.A.S. This"dropping run" is of significance only when carrying the 20 external containers.In this configuration and using 200 flap, a boost pressure of about - I lb/sq.in.was required to give the desired I.A.S. of 115 knots. Polar diagrams for thiscondition (fan off Nos. 1, 2 and 4 installations) arc shown in Fig. 10. Cylin-der temperatures wore high, rcquiring half gill opening on some engines to keupwithin the limitations of 30000.

5. Discussion of results

5. 1. Effect of removi., cooling fans on cylinder temperatures. The

effects are summarised bcla;:

Containers not fitted

Increase in max: cyl: I

Test conditions tmp: due to removingi Number of hottest cylinderfans (00) _

No.1 Eng. No.2 Eng.No

Manoeuvre Gills. No. No. !No. I-lean Fan Fan Fan Fan Fan Fan_ ir Intake I 2 4 Inc. ON OFF0 ON OFF ON [OFF

Ground cooling 0en.at 1400 r.p.m. Clean. 20 5 25 15 2 12 1&7 12 2 12

Take-off atsafety speed; 0.on.take-off power. Clean. 15 15 20 15 12 12 8 2 12 14

Climb at 125 -

kts. at 4,500feet. (near end Open. I0 25 10 15 2 2 3 2 12 14

of 5 mins; Clean.take-off power.

Climb at 130kts. at 3,000feet; inturmc- Open. 0 -10 10 5 14 14 1 1&2 14 114iate poior. Ram. I

Level flight atI8,000 feet;max. continuous Shut. 10 15 0 10 2 2 1 1 2 2&1power, weak Ram.mixture. _,_ _.__,

These results are in good agreement with those obtained on other comparableinstallations at the A. & A.E.E.

5.2. Comparison of cylinder temperatures measured by the standard and

test pyrometers. A comparison is made, using notation as follows:-

A. Cylinder head temperature of No. 14 cylinder measured by the Standardsingle point pyromoters.

B. Cylinder head tomorature of No. 14 cylinder measured by test -pyrometers.0. Cylinder head temperature of the hottost cylinder, measured by test

pyrometers.

/cooling....

-8-

0ooling fans off Noa. 1, 2 and 4 engine installations, gills fullyopen except in level flight at 8,.000 feet. when they were shut: -,

Containers not fitted.

A -B(C)-_ _ A -C(C) ..Manoeuvre Engine No. Mean Engine No. Mean

1 2 3 1 Value 1 2 13 Value

Ground run vt

11400 r.p.m. -15 -15 0 -20 -10 -20 -25 -5 -30 -20

Take-off at safetyspeed; take-offpower. -25 -30 0 -15 -15 -35 -35 -10 -15 -25

Climb at 1 25 knotsat 4,500 feet,(near end of 5 minstake-off power. -35 -20 -10 -20 -20 -45 -50 -25 -20 -35

Climb at 1 30 knotsat 8,000 feet;interimediate power. -35 -30 -10 -15 -20 -35 -35 -10 -15 -25

Level flight at8,000 feet; rmax.continuous powier,weak mixture. -30 -35 -10 -10 20 -55 -45 -30 -10 -35

The mean values of A - B are similar to results obtained on a Hastings

aircraft powered ith Hercules 101 engines at A. & A.E.E. and T.E.U. (See 17th

Part of JdE/83). The tests on that Hastings aircraft also showed that num-ber 14 cylinder, to ahich the standard pyrometer was fitted, was not the

hottest cylinder in every case; a sidlar result was obtained on a Varsity.

(See 7th part of 213/373),

The reasons for incorrect indications of cylinder temperatures givenby the single point pyrometers is not known to date; this is to be the subjectof a separate investigation.

It is significant, however, that the errors (mean values) in cylindertemperature indications tend to become greater vrith progress of the flight plan,

i. e., the errors arc a minimum during the ground run, rising to a maximumn beforethrottlin-back to continue the climb at intermediate porter, and thereafterremaining sensibly constant. This characteristic of error may be due to the

influence of temperature gradients and changes in those gradients, across the

fireproof bulkhead (which carries a form of plug and socket connection for thepyrometer leads), reacting unfavourably on the electrical characteristics of

the pyrometry. The basis for believing that there are material changes in

teiperature gradient is founded on the supposition that the engine bay forwardof the fireproof bulkhead is being generally heated as the flight progresses,until it reaches a near stable temperature around the throttle-back point on

the climb, while the temperature to the rear of the bulkhead remins sensiblyconstant at a materially lowier teimiperature. The effect of such unequal heat-ing on the behaviour of the pyrometry will be included in the investigation

referred to above.

The potential dangers of incorrect indications (negative errors) of the

hottest cylinder temperature of the magnitude shown above (A - C) would appear

to be obvious. The follving is indicative of those dangers.

(a) It is assumed that, among other reasons, the pyrometers are installed

for use by aircrw as a .,uide as to when to adjust the aowl gills to keep the

cylinder temperatures within the pruscribed limitations; observing the

/principles....

-9-principles that minimum gill opening, cormensurate with cooling requirements,should be used for reasons of aerodynamic cleanliness and hence optimum per-forxance. If such a procedure is used in the Service, it would be reasonableto expect serious overheating of the engine, in terms of the cylinder tanperr-ture limitations declared for the Hercules 106 engine, particularly with theaircraft carrying external stores in hot climates. 4

(b) Transport Commwand would appear to be justified by their multitudeof indications of cylinder temperature observed during operations of Hastingsaircraft in hot climates in believing that the cooling level of the Hercules106 engine is quite adequate for operating under conditions of high air ter,-perature. This belief could be such that, if the failure rate of cowl gillcomponents (e.g. ,ill motors) becomes unreasonable, they may decide to makethe gills inoperative, i. e., fixed in the closed position. The dangersattondant upon such a hypothetical case are again evident in terms of thelimitations declared for the Hercules 106 ongino.

5.3. Positioning of single point pyrometer. It is clearly impracti-cable to select any one cylinder that is always the hottest under the vary-ing conditions of operation, since changes in teqmerature distribution arebrought about by such factors as:-

a changes of enpine setting at constant height,b danges of heigh)t at constant earnine setting,

changes in ambient air tererature,d changes of .7ill scttin--,

e engine tuning tolerances.

Furthernore, variations of temperature distribution vill undoubtedlyoccur bebteen nominally identical engines and/or by virtue of different loca-tions on the aircraft.

The results of the present tests have, however, been examined to deter-rne if number 14 cylinler is the best choice for indicating the highestcylinder head te-crature under the conditions of test covered in this report.This results in the followvirg:

(i) Usiniz all the results, fans on and off. The cylinder which moreoften experiences the hihost temperature, is No. 2; it is not, ho;ever,greatly superior to l. "14.

(ii) Using the results with fans off. The result is similar to (i),but with greater emphasis on No. 2 cylinder as the more representative cylinder.

(iii) Us_in only the results of the two most critical working cases,fans off. Number 2 cylinder is the hottest in both instances.

The foregoing agrees with somew:hat meagre results obtained at this Establishmenton other similar engine installations.

5.4. Assessment of suitability of cylinder cooling for operating underconditions of I.C.L.N. , tainperato summer, and tropical summer stan-dards of air ternerature, in terms of the current cylinder tern-perature limitations. The following is to be noted in relation

to this assessment:-

(i) Tests on 'JD.476 were, in general, intended to be made with anexternal configuration representative of the worst drag case, e.g., two Jeeps

and six containers carried externally. Circumstances iade it necessary, however,to approximate to that condition on test, by the carriage of twenty containers.The aircraft's performance in each of these configurations is given in the 4thPart of MIAE/843/1/P. That data has been used as a basis for estimating theeffect of the reduced performance due to the carriage of the mixed load of jeepsand containers, on cylinder cooliiV,. This results in:- /(a) ....

.. :- 150 r~t sea lrcl with ru:sociatcd lapsc rate.

Teperate Suj'.,r:- 270r at sea level vith associated lapse rate.

Tropical Su-ner:- 41,C at sea level with associated lapse rate.

(a) negligible effect on cylinder tomperaturos during ground running,~~tako-off, and climb.

(b) a rise in cylinaer temiperatures of about 50, in level flight at

8,000 foct at maximum continuous power (weak mixture) and in* level flight at I ,000 foot usinS a power scttiAr to achieve the

desired dropping spoo,! of "115 knots, I.L.S.

The assessment of the suitability of cylinder cooling includes anallowance for (b).

(ii) Tests made over a range of air temperature on other engine instal-lations, indicates that the correction to cylindcr teporature for air tempera-turo will not be loss than 1.0 LTP when using cruisin, powers in the weakmixture range, and is probably of the order of 0.7,T at take-off and inter-mediate powers.

The assessmcnt is therefore given on the basis of:-

(a) 1 .0 AT for all tests; this comforms with the present requirementsof A. P. 970.

also (b) using 0.7 LT for those tests at take-off and intermediate powers.

The assessment is made in tabular form below, as the differences (to thenearest 50C) between the temperature of the hottest cylinder of thehottest engine and the appropriate limitation, for the three standards of airtemperature.

"M1" Sup ercharger

Difference bet-ieen hottest c linderTest conditions temPerature and limitation. C.

0 owl Temperate Tropicalgills IExt.R ! Fans N Suirier Simer

Manoeuvre Power and j load I onTISottinglair ion or or T.C.L.N.1.0&1 0.7L\,T .O'T 0.7Ll

'intake off .off 1

on attaininj Take- Full On or On -25 -15 -5 0 -5safety speel off bpan. Off Off -10 0 0 +15 +110at take-off Clean.

(125 kts.a. ___

Climb at4,500 ft. at Take- 1Full125 kts.j.I•.,S.off Jopen. On or On 0 +10 +10 +25 +20

(towards end Clean. Off Off +10 +20 +20 +35 +30of 5 win.from startof take-off.) .__Climb at8,000 feet Inter- Fullat 130 kts. mediate open. On or On -15 -5 -10 +10 +5I. A.S. , ]Ram. Off Off -5 +5 0 +20 +15

(Shut. Off On -25 -15 0Level flight Max. IRa. ]Off Off -20 -10 + _

at 8,000 contin. Full Hfeet. (Weak open. IOn Off -5 +5 +20lax.)_Ram. 1__ __.C

Level flight At appro-at 1,000 ft. priate Halfat dropping power, open. On Off +5 +15 . +30speed of weak Rm. 0115 kts,!.A.&ra ixture. ,

/Contd .....

- ,T . the difference between the standard air temperature and the ambientair temperatures on test.

External load assumed to be 2 Jeeps and 6 containers.Z These results are factual (the air temperature on test did

not differ from the I.C.A.N. standard by more than + 300).

It is possible that Transport Command, in their routine operation ofHastings aircraft, do not invoke the use of take-off power for a period grea-ter than that necessary to achieve a safe height following take-off, (up toabout 100 feet) , the engines then being throttled back to intermediate poer.It is estimated that, under those conditions of operation:-

(a) the maximum cylinder temperature at the throttle-back point wouldbe about 500. greater than that obtaining at the take-off safetyspced.

(b) considerink the take-off and climb to 8,000 feet as a whole, themaximum amount by which the temperature of the hottest cylinderwould exceed the limitation with fans off, will be reduced to some15 to 2000 under tropical summer conditions.

On the other hand, such a relaxation in cylinder temperatures would notbe valid under circumstances such as an engine failure occurring on take-off,or when practising overshoots with simulated engine failure.

Tests on similar installations at this Establishment have shcwn thatopening the gills fully at constant power setting is not necessarily the bestmethod of achieving a reduction of cylinder temperature in level flight. Itwas found from these tests that, for the same loss of speed arising fromopening the gills fully at constant throttle setting, a greater reduction(approximately 500) of cylinder temperatures was obtained by throttling backrith the gills shut. The adoption of such a procedure in lieu of using fullgill opening in level flight at 8,000 feet should produce a similar beneficialresult.

In the case of level flight at 1,000 ft., when it is required to achievea speed of 115 knots, the combination of power and gill settin3 used is con-sidered to approximate closely to the optimum for cylindur cooling. Thecharacteristics of the gills are such that opening than beyond the positionchosen (half open) would result in a fairly rapid increase of drag accompaniedby an insignificant improvement in cylinder cooling at constant engine setting.Since increased power will then be required to maintain the speed of 115 knotsI.A.S., this would probably result in higher cylinder temperature.

6. Conclusions

6.1. Standard sin-lc point pyrometers, and their location. The cylinderhead temperature of No. 14 cylinder, to which the standard single point pyro-meter is fitted on each engine, is incorrectly indicated by the standardpyrometer. This equipment indicates a cylinder temperature some 200C, lowerthan that measured by test equipment.

No. 2 cylinder waould be a better choice than No. p1 , for locating thesingle point pyromters, in ters of a cylinder which is most frequently thehottest cylinder under all the various conditions of operation.

The potential dangers associated with the unreliability of the presentsingle point equipient, coupled with the impracticability of selecting asingle cylinder which is always the hottest under all conditions, warrants con-sideration being given to the deletion of that equipment in its present formand the institution of a suitable drill for manipulation of the gills in termsof operating conditions and ambient air temperature. When the reasons for themal-functioning of the single point pyrometers is known, and cures effected,the re-introduction of single point equipment would be justified; it shouldbe located on a cylinder which is the most representative of the hottestcylinder for those concitions of operation givin3 rise to the highest criticalcylinder temperatures.

/6.2 ....

I _

-12-

6.2. Suitability of' cylinder cooling in term of the current cylinderta ajorature lirnitations. Aftur taking into account

(i) the probjable matwier in which Has bings aircraft carrying external,

stores are oporated by Transport Comirand,

(ii) mothofs of obtaining optimum cylinder cooling,

(iii) corrections wvhich are a closer approximation to the true -rate ofchange of cylinder temporature ith air temperature,

and (iv) an external load representative of the worst drag case,

it is concluded, from the tests on ',D.476 with cooling fans removed, that thecurrent cylinder temperature limitations will be exceeded under tropical sum-mer conditions by:-

b Climb 150C( Level flight at 8,000 feet 150Cd Level flight at 1 ,000 feet, (dropping speed 115 knots) 300C.

With the cooling fans fitted, (d) is the only case likely to give riseto the limitations being materially excaedcd, i.e., by about 15 to 200C.

The frequency ith which mchanical failures of the cooling fan instal-lation has occurred on Hastings aircraft operated by Transport Command, suggeststhat their retention may intrcluce a hazard greater then that due to the increaseof cylinder temperature arising from their removal.

6.3. Suitability of the cylinder cooling in terns of the experienceobtained in Transport Command. It appears that Transport Command

is successfully operating Hastingqs aircraft powered with Hercules 106 engines,without cooling fans, under near tropical conditions. Those operations havepresunably included Hastings aircraft in configurations similar to the worstdrag case e.g. two Jeeps and six containers.

If this is correct, then,

(a) on the basis of the results obtained on 'JD.476

(b) assuming the conditions of test on YD.476, ccrnbined with the relevantassumptions made, reflect the manner with which Hastings aircraft areoperated by Transport Command,

and (c) assuming that similar low indications of cylinder temperature aredisplayed to the operators by the standard single point pyrometers(which may lead to the gills being closed when they should be open),

then it would appear that cylinder temperatures materially higher than thecurrent limitations have occurred on numerous occasions.

This would be expected to give rise to an increase in the rate of engineor relevant component failure. To the best of our knowledge, however, this hasnot occurred. U7e would therefore suggest that, on the basis of-the foregoing,the cylinder temperature limitations declared for the Hercules 106 engine canbe materially exceeded with safety.

7. Further developments. kIm investigation is proceeding into the reasons for the apparent mal-

functioning of the standard pyrometer equipment.

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Defense Technical Information Center (DTIC)8725 John J. Kingman Road, Suit 0944Fort Belvoir, VA 22060-6218U.S.A.

AD#: AD 020259

Date of Search: 18 November 2008

Record Summary: AVIA 18/3015Title: Hastings Mk2 (4 Hercules 106): engine cooling tests at 80,0001b with and withoutcooling fans and external storesAvailability Open Document, Open Description, Normal Closure before FOI Act: 30 yearsFormer reference (Department) 843/1 PT9Held by The National Archives, Kew

This document is now available at the National Archives, Kew, Surrey, UnitedKingdom.

DTIC has checked the National Archives Catalogue website(http://www.nationalarchives.gov.uk) and found the document is available andreleasable to the public.

Access to UK public records is governed by statute, namely the PublicRecords Act, 1958, and the Public Records Act, 1967.The document has been released under the 30 year rule.(The vast majority of records selected for permanent preservation are madeavailable to the public when they are 30 years old. This is commonly referredto as the 30 year rule and was established by the Public Records Act of1967).

This document may be treated as UNLIMITED.