passengers will be competentprofessionals in their own field andwill be used to helicopters, probablyflying with several companies asidefrom yours. All they will beinterested in is safe transport, so givethem a smooth flight and a goodbriefing. Word gets around.Avalanche ControlThis involves applying explosivecharges to selected places in anavalanche start zone, so you needpermission to carry DangerousGoods. You must be precise, andthere will be a qualified Blaster(Bombardier) on board to dispensethe explosives, who will have a bodyharness secured to the helicopter intwo places – it must not have aquick-release mechanism. The doorswill be off, so you need to dressproperly and watch your speeds andC of G, especially lateral. In fact, theweight of explosives and peoplerequired for the job must not bemore than 75% of the usefulpayload. Ski baskets, or any otherrestrictions to dropping must beremoved beforehand.The area should naturally be closed.Primers must be prepared beforeentering the aircraft and pull-wirescarried separately – none are to beadjusted inside, and they are toremain in the same container at alltimes. Only the explosives to beused on a particular sector should becarried, and they must be pushedaway from the bombardier’s seatSpecial Use Of Aircraft 243position where you can see them,not above, behind or below. Youhave 90 seconds after dropping thefirst bomb to do the rest before youmust pull away to a safe area forobservation. If there is no assistant,that is, just you and the bombardierare on board, you can only dropthree charges anyway.Aerial HarvestingRemoving tree crowns or conesfrom standing trees with ahelicopter, for monitoring theprogress of growth, insect or diseaseinfestation, and pesticide or fertilisertrails. There are two ways of doing it.The first involves an unmanneddevice underneath the machinewhich uses the downwash toseparate foliage from the tree, whichends up in the device. A BranchCollector cuts branches from the mainstem, a Rake collects cones bystripping them from the foliage withstationary or moving tines, and a TopCollector takes away the upper portionof the tree crown.The second is really aerial clipping,since it is done by someone from therear door with an battery-poweredelectric chainsaw while you hovernear the top of the tree. Whatever iscut ends up in the helicopter, sothere is a barrier between the twoparts of the cabin so you don’t get abump on the head. Believe it or not,this was originally done with a steelbox with retractable doors, the edgesof which cut the tree as the box waslifted up from it, but it proved to beslow and cumbersome, and strainedthe equipment too much.
As well as the clipper, there is anavigator to tell you where to fly,since you will be busy enough at thatlevel. Don’t expect to fly more than6 hours a day, or in wind over 15 kts.The aircraft itself must be on lowskids, with no bear paws, or itemsthat can get caught. You yourselfmust be an ace at long-lining, with atleast 1000 hours on type.You start off with a hoversomewhere between 25-50 feetabove the trees concerned, using upto 85% torque, so you’ve got areserve. Keep them between yourright shoulder and just forward ofthe front edge of the front door.Then descend to within eye level ofthe target, always being aware thattrees sway in the wind and you caneither get hit by another or hitsomething else as you try and keepup with the tree you are workingwith (your downwash won’t behelping). Its top should be level withyour eyes or the cabin roof, slightlyforward of your right shoulder.Don’t fixate on the tree top, butsomething else that isn’t moving.Slide the skid in between thebranches until the stem of the tree isagainst it, using a little collective justbefore contact. Then lower thecollective so the skid rests againstthe lower branches to keep it steadyfor the clipper, who shouldn’t takemore than a minute to do what’srequired. Before you move away,check the skid isn’t caught onanything, then increase collectiveand use left cyclic to pull you awaygently. Don’t move directlysideways, as upwards slantingbranches near the tops of trees couldsnag you.A couple of points to watch – if youbend a tree beyond the cyclic stops,when it rebounds you will be out oflimits as you try to correct things.244 Operational FlyingYou will do best to keep level anduse left cyclic with the rebound.Don’t go straight up or you mightget dynamic rollover. Trees withbent tops indicate heavy crops andshould be avoided, because they willhave too much momentum. If youhave to work round a tree top, hoveraway and assume a new positionevery time rather than spinninground it.Wildlife CaptureNormally done with a pilot andgunner (who has a net gun), butthere may also be an assistant (calleda mugger) as well. If there isn’t, andyou have to do the job instead, youshould only handle the head of theanimal, so you don’t get injuredunnecessarily. Your briefing shouldinclude getting in and out of thehelicopter whilst in the hover.A slightly forward C of G ispreferable. Keeping the rotor disc asflat as possible, and avoiding tightturns, approach the animal frombehind, slightly away from the skidand forward of the gunner, almostdefinitely with a sideslip. Don’tfixate on the animal, but keep it inview with peripheral vision. Thereason for the flat disc is to keep it
out of the line of fire, and high-Gturns will upset the gunner’s aim.Sometimes the wildlife will be seals,so you have to wear lifejackets andstuff, and dodge the waves whenthey get a bit big (sometimes youhave to use the waves to get youback in the air again).Helicopter Instrument FlyingThis is much the same as for fixedwing, but there are a couple ofdifferences worth noting. Firstly,thrust and lift come from the samesource, that is, the main rotors, soyou can have different attitudes thanexpected when climbing, descending,or in level flight, so you need tolearn particular power settings forparticular stages of flight to do itcorrectly. These, of course, arecontrolled by the collective anddisplayed on the torquemeter. TheAI indicates fuselage and not disc attitude,so does not always tell you what theaircraft is actually doing – you couldbe nose-up and still descending at 60kts, so more cross-checking withother instruments is required thanwith a fixed wing aircraft. Putanother way, while it is stillimportant, the AI loses a little of itsdistinction.Also, the ability to fly at low speed,say, below 60 kts, means that thepitot-static instruments become lessreliable. You also get reducedstability, which is why there is aminimum IMC control speed (Vmini),below which you shouldn’t go intocloud, as well as minimum speedswith one engine out, should youhave two.Having said that, the attitude + power= performance equation is still valid.Techie StuffAn Ops Manual, despite theadoption of the Flight Manual aspart of its structure, will need aTechnical Section dealing withaspects peculiar to the Company'stypes of aircraft (that is, Part B). Youmay feel you've been taught enoughof it already, but things like oil andfuel requirements and specimenperformance data will still need to beemphasised. Also, the checklists inthe usual standard of Owner'sManual are nowhere near goodenough for Commercial AirTransport, so these will need to beexpanded, too (they never seem tograsp the idea of battery saving, asthe Master Switch is often the firstthing to be switched on and left onfor the next 10 minutes while youcheck everything before starting anengine).Whilst not too much informationshould be duplicated between theFlight and Operations Manuals,enough ought to be included thatmay be relevant in flight withanything of a detailed descriptivenature left in the Flight Manual. Thisis important in smaller aircraft withno room for a complete library.Topics to be covered includecrosswind take-offs on ice coveredrunways, action not included inchecklists or drills, special handlingtechniques and other stuff that needsto be brought to your attention. Try
placing emergency drills on differentcoloured pages.If you haven't thought of it already(because most pilots tend to bemechanically-minded), it will be wellworth your while digging a littledeeper into engineering principlesand practice in general. Not only willit help you stay alive, but you getmore out of engineers when youspeak their language. Having saidthat, engineers speak in a veryprecise manner—to give you aflavour, try reducing the descriptionof a piston to just three words (onesuggestion is a sliding, gastight plug).Just for fun, here is a selection ofreplies to pilots’ comments onreturning from test flights in theUSA. They are known as SQUARKS246 Operational Flyingand are left for maintenance crews tosort out before the next flight.Test flight ok, except auto land abit roughAuto land not installed on this aircraftDME Volume unbelievably loudVolume set to a more believable levelFriction locks cause throttle leversto stickThat's what they are there forNumber 3 engine missingEngine found on right wing after briefsearchTarget radar humsReprogrammed Target radar with thewordsAircraft handles funnyAircraft warned to straighten up and beseriousLeft inside main tyre almost needschangingAlmost replaced left inside main tyreEvidences of leak on right maillanding gearEvidence removedIFF inoperativeIFF always inoperative in OFF modeSomething loose in cockpitSomething tightened in cockpit.Leading Edge Protective TapeProtective tape is used on leadingedges of rotor blades (and somepropellers) to protect against wearand tear from dust or precipitation.A partial loss of it can dramaticallyaffect aerodynamic efficiency,resulting in substantial increases inpower when hovering. It will alsocause a slight loss in RPM duringautorotation.The most likely time for the stuff tocome off is during or after flightthrough rain, which is just when it'sneeded, so check it before take-off.If it looks like wearing out, removeor repair it before the next flight,removing an equivalent amountfrom each blade, as it may have alsobeen used for balancing. It will beput on in short strips of anythingbetween 6-18 inches (so you're notflying with a great length of ithanging off) which should beremoved as a whole—don't just cutbits away.If tape comes off in flight (with adistinctive "chuffing" sound,sometimes accompanied by verticalbounce), reduce power and speedand make gentle manoeuvres whilelanding. If it comes off before
landing, just carry on.Propeller OverspeedIf engine control is lost and RPMrises above the maximum, reducepower, raise the nose and hopereduced airspeed gets things undercontrol. If the CSU is not working,feathering immediately may leaveyou with a shut down engine in fullyfine pitch, though it does depend onthe aircraft (Doves, apparently, havea separate feathering motor).If you're not quick enough, damagecould be caused from over-revvingand the feathering system may notcope with the extreme RPM. DONOT attempt to unfeather theengine but land as soon as possible.Techie Stuff 247Failure of Feathering SystemMost feathering systems don'tfunction below a certain low RPM(typically 700-1000), so you don'tstart with the blades feathered.However, there are furtherimplications—if your engine failsthrough a major mechanical fault,you may not be able to catch thepropeller quickly enough. The usualreaction is to close the throttle of thedead engine first, so opening it alittle may increase the RPM forfeathering to take place properly.Keeping your speed up may help aswell.If the propeller fails to feather,reduce your airspeed to a minimum(but not below scheduled engine-outclimb speed) and allow the RPM tostabilise as low as possible. Tryagain. If feathering still fails, try toreduce speed so the rotation ceases,which will cause less of a dragpenalty than a windmilling prop,even if it has stopped in fine pitch.Not only will your single-enginedclimbout performance be affected,directional controllability will be,too, though you should be OKdown to Vmca.TwinsFlying twin-engined helicoptersrequires a different philosophy inmany ways, certainly getting used tonot dumping the collective everytime an emergency happens, andtheir complexity, although there isno real change in flyingcharacteristics as there would be ifan engine fails in an aeroplane. Youalso have takeoff and landingprofiles, in case something happens,and performance charts, withgenerally more shallow approachesto comply with them.The regulations require you toensure that your aircraft hasadequate performance for anyproposed flight. The "performance"of an aircraft describes its ability tomaintain certain rates of climbagainst distance, so you can avoidhard objects (obstacles), particularlywhen you can't see them. As a result,the charts will emphasise rates andangles of climb very strongly (climbrequirements are established withone engine working hard for aspecified time).There are reasons for multipleengines, of course. One is that youget more power and can lift more,but another is for safety – failure ofan engine should not affect thecontinued safe operation of theflight, or the other one, which is whythere are isolation arrangements inthe engine compartment. It follows,therefore, that the less the weight ofthe machine, the better it can flywith less power. In fact, withreference to the profiles above, youmay find different max all-upweights for helipads and clear areas(there is no definition of a "helipad"for performance purposes – rather,it's any area that isn't a clear area, orone that allows operation inside yourchosen performance group).The take-off and landing phases ofany flight are the most critical,demanding the highest skills fromcrews and placing the most strain onthe machine. Because of this, strictregulations govern the informationused for calculating take-off orlanding performance. Of course, inthe old days (say during the war, orwhen the trains ran on time), having248 Operational Flyingenough engines to lift the load wasall that mattered and no priority wasgiven to reserves of power and thelike. Now it's different, and you mustbe able to keep your machine aspecified distance away fromobstacles and be able to either flyaway or land without damage topeople or property (and themachine) if an engine fails.Performance requirements will beworked out before a C of A isissued, over a wide range of
conditions. They are subsequentlyincorporated in the Flight Manual,which forms part of the C of A.Helicopters are certified in one ofseveral groups. For example, JARclassifications are 1, 2 and 3, whichare broadly equivalent to the UKGroups A, A(Restricted) and B (seethe table below). It is important torealise that these are different fromAirworthiness groups, which dictatehow well the airframe stands up to aforced landing.Passengers JAR Class UK AN(G)ROver 19 1 A9-19 2 A (Rest)*Less than 9 3 B***Up to 15 passengers and 12,500 lbs** Less than 6,000 lbsJAR Class 1 (Group A) helicoptersrequire no forced landing provisionsif an engine fails. Class 2 machineshave a limited exposure (that is,occupants and third parties mustremain uninjured), while Class 3types have to make a forced landing.Single-engined helicopters thereforecome under Class 3. In addition,Class 2 ops must be done underconditions that allow a safe forcedlanding, in terms of weather, lightand terrain – those done fromelevated pads in non-hostileconditions must be done by dayonly, otherwise you must abide byClass 1. Class 3 ops must be done insight of the surface, by day, with atleast a 600-foot ceiling. Theminimum visibility is 800m.The screen height for JARs is 35feet, for takeoff and landing. Thereare no distance requirements.Group A helicopters must (with oneengine out) clear all obstacles underthe departure track within a definedarea by a specified margin. In fact,they should be able to climb (afterCDP) at 100 fpm to MSA with thegear down (most unfavourable C ofG), then continue at 150 fpm toMEA with One Engine Inoperative(OEI). Naturally, if the remainingworking engine is not powerfulenough to lift the weight, the flightwill not continue, so, as with fixedwing, there is a point during thetakeoff procedure at which, if anemergency happens, you elect tocarry on or reject, called,unsurprisingly, the Critical DecisionPoint, or CDP, which is the onlypoint at which you have two choices.Which group you belong to dependson Certification, Max All-Up Weightand the number of passengerscarried, although the JARclassifications are based on the latter(see below). However, it may bemore acceptable commercially tooperate in a lesser group if it enablesyou to take more payload, and makemore money – all you might need islonger takeoff runs or less obstacles.In other words (just to reinforce thepoint), the conditions under whichTechie Stuff 249you operate determine how heavyyour aircraft can be and, as a result,your payload. Over a whole trip, theweight could be dictated by:·
Maximum weight
·
WAT limits (see below)·
Space available·
Obstacles·
The route·
Hovering OGEIndividual machine performance willvary due to such variables as the ageof the airframe and engines, thestandard of maintenance, or crewskill and experience, without theengines being adjusted for severalseconds after the initial failure. Whatyou can do on one day under a givenset of circumstances may well beimpossible another time.Performance is therefore a set ofaverage values—particular machinesmay be better or worse.The original testing, of course, isdone with new aircraft andexperienced pilots, which are knownas unfactored. Fudge factors areapplied to unfactored figures toproduce net performance (and grossperformance when they're not), sothere is a margin if you have a tiredengine, or a new pilot. Occasionally,performance data (as amended) in aflight manual will already befactored, but you will have to checkthe small print on the chart, in casethey surprise you (JAR does notmake a distinction between the two,except for a 1% margin for IFR).Also, figures and graphs are basedon Standard conditions which allowfor fixed reductions in pressure andtemperature with height. As we allknow, the real world isn't like that,so these assumptions may not alwaysbe true and due allowance musttherefore be made for them (if youraircraft is performing sluggishly, youmay find it's not the machine, butthe conditions it has to work underthat are at fault).ProfilesA profile is a series of target steps tobe achieved on takeoff or landing,designed to give you the best chancein an emergency. For example, witha TwinStar in a clear area, you wouldgo up to 6 feet, then nose forward to10 feet and 30 knots, (CDP)accelerate to 40 kts (VTOSS) up to 550feet, level out and accelerate to 55kts (VY):In practice, with both enginesperforming normally, you wouldaccelerate as quickly as possiblethrough CDP and climb away as youwould with a single – only if anengine fails would you decelerate toVTOSS, or Takeoff Safety Speed (theequivalent to V2 in a plane, for thebest angle of climb, then adopt VY atthe prescribed height, for the bestrate of climb.The CDP is the only point whereyou have a choice of action – beforethen, you reject. Afterwards, youcarry on. The LDP is a similar pointfor landing, where the idea is to hit aspeed and height combination fromwhere you can make an approach250 Operational Flyingthat will allow you to land safely(most people get to one first, thencreep up on the other).There can be many variations on theCat A theme:
·
Airfield, or Clear Area, withdistances around 1000-1500 feetto play with, accelerating towhere you can climb even atmax weight, usually close to VY.·
Reduced Field Length, climbingvertically or even backwards, toland in a much smaller area ifyou have to, say 300-500 feetlong, usually at about 85-90%max weight.·
Vertical, which speaks for itself,but you may have the option ofa dip below heliport height ornot (i.e. at ground level). Theformer allows 90% max wt, thelatter around 80%Class 1 helipad take-off proceduresinvolve climbing vertically at first,then going upwards and backwardsto a predetermined height (theCritical Decision Point, or CDP) beforegoing forward (actually, ICAO nowcall it the Takeoff Decision Point, orTDP). This could be up to 150 or200 feet above the helipad, aftergoing vertically to about 50 feet first(if you've got the power on a hotday!). For the TwinStar, you startgoing backwards from about 15 feet,at around 200 feet per minute,keeping the helipad in sight, and atTDP (90 feet) select max power and10° nose down at the same time, soyour tail doesn't hit anything.In theory, having moved backwards,you still have the take-off spot insight and it's therefore available forlanding. At CDP (or TDP), if youelect to carry on to forward flight,you should be able to clear thelanding spot during the steep diveyou have to make to achieve flyingspeed, which is why the CDP isabout 40 feet high. Once you'rehappy about the power, gentlyaccelerate level, to VY.All this is not without its critics,though, since prolonged hovering athigh engine power is not necessarilygood engine handling. Not only that,it may be impractical on an oil rig ifthere are accommodation blocks andcranes around.Unofficially, therefore (from a riganyway), one school of thoughtsuggests a level acceleration to bestrate of climb speed, then going up toa safe altitude, whereas othersadvocate getting to best angle ofclimb speed, climbing to a safeheight and then accelerating to bestrate of climb. The first is supposedto keep you in the H/V curve less,but the second gets you highersooner, so you lessen the chances ofhitting the water if an engine fails,especially if the deck is only 50 feethigh (most major platforms are 100feet off the water).One technique might be to hoverover to the front of the deck withthe rotors not overhanging (the frontis where the wind is coming from).Check the Ts & Ps as usual, thenpull power and head upwards,rotating while there is a positive rateof climb to a few degrees nose down(10 is OK initially - you might loseheight with more), to get the tail upand clear. After rotation, maintain
the collective while looking fortakeoff safety speed and accelerate.Techie Stuff 251As to which technique is best, youhave to make some choices yourself,like whether you want to hit thewater or the deck, or would ratherbe low with rotor RPM, or higherwith less, and little airspeed.To get back on to the ground, youwill not be surprised to hear there isa landing profile as well, for theTwinstar being something like this:For a clear area, you arrive at the100' point at 40 kts (it's actuallydifficult to get them both at thesame time, so you would first hitone, then the other). For a helipad(that is, not within the definition of aclear area), the figures are 90' and 30kts, for a semi-vertical arrival.Factors Affecting PerformanceDensity AltitudeThis is the altitude at which the ISAdensity is the same as that of the airin question or, in other words, yourreal altitude resulting from theeffects of height, temperature,pressure and humidity, all of whichcan make the air thinner and whichare mentioned below. The detailswill be in the Flight Manual,although humidity is usually ignoredin the average performance chart,because it has more to do withengine power than aerodynamicefficiency, and high air density andhumidity do not often go hand inhand. However, if the air is humid,say after a good shower, you wouldbe wise to be careful.Anyhow, the idea is that the morethe density of the air decreases forany reason, the higher your aircraftthinks it is. If you look at the liftformula, you will see that the liftfrom a wing or thrust from apropeller is directly dependent on airdensity, as is drag, of course. Theeffects are as valid at sea level as theyare in mountainous areas whentemperatures are high – for example,90° (F) at sea level is really 1900' asfar as your machine is concerned. Inextreme circumstances, you mayhave to restrict your operations toearly morning or late afternoon.Here is a handy chart:°F/C 60/15.6 70/21.1 80/26.71,000’ 1300 2000 27002000’ 2350 3100 38003000’ 3600 4300 50004000’ 4650 5600 63005000’ 6350 6900 76006000’ 7400 8100 88007000’ 8600 9300 1,00008000’ 9700 10400 111009000’ 11,000 11600 124001,0000’ 12250 13000 1360011,000’ 13600 14300 1500012000’ 14750 15400 16000It shows that, at 6,000 feet and 21°C,for example, you should enterperformance charts at 8100 feet.TODR will increase by 10% for each1000-foot increase in aerodromealtitude and 10% per 10o C increasein temperature (factor by 1.1).252 Operational FlyingLDR will increase by 5% for each1000-foot increase in pressure
altitude and 10o C increase intemperature (factor by 1.05).Aircraft WeightGreater mass means sloweracceleration/deceleration and longerdistances. TODR will increase by20% for each 10% increase in weightand LDR 10% per 10% increase inweight (factor by 1.2 and 1.1). Veryfew aircraft allow you to fill all theseats with full fuel.Some manuals give take-off andlanding weights that should not beexceeded at specific combinations ofaltitude and temperature, thusensuring that climb performance isnot compromised. These are knownas WAT limits (Weight, Altitude andTemperature)Dynamic RolloverThis occurs when your helicopterhas a tilted thrust vector with respectto the C of G, commonlyencountered with some side driftwhen you have one skid or wheel onthe ground acting as a pivot point,but you can also get a problem whenyour lateral C of G falls outside thewidth of the skids or wheels. Everyobject has a static rollover angle, towhich it must be tilted for the C ofG to be over the roll point, for mosthelicopters being 30-35°. As yourlateral cyclic control at that point is alot less effective than if you werehovering, because it is not rotatingaround the C of G, but the rolloverpoint, you have less chance to getout of trouble, and the only effectivecontrol is through the collective (donot raise it). In other words, the liftfrom the rotor disc that should bevertical is inclined and convertedinto thrust, above the centre ofgravity, so trying to use the cyclic tolevel, and the collective to get youoff the ground is wrong!Dynamic rollover is worst with theright skid on the ground (counterclockwise main rotor) and with acrosswind from the left, with leftpedal applied and thrust about equalto the weight (i.e. hovering). Amachine can roll upslope if youapply too much cyclic into it, ordownslope if you apply too muchcollective, enough to make theupslope skid rise too much for thecyclic to control. Avoid it by keepingaway from tail winds, and landingand taking off vertically.Engine Failure andAutorotationsThis part is not meant to cover(again) the basic stuff you learn inflying training, but to offer advicethat would be useful to a workingpilot, who is very often over trees, orin remote places that the student isroutinely taught to avoid. In short, ittalks about surviving a potentialcrash, because you won't always findyourself over the clear areas youneed for training.Engine failure in a helicopter isdetected by a noticeable decrease inengine noise (!), yaw in the samedirection as blade rotation, loss inheight/speed and RPMs, plusENGINE OUT audio/visualwarnings (if fitted), because there'sso much noise you can't tell whether
