Airplane Takeoff Speeds Are Designed To Ensure The Liftoff .
Airplane takeoffspeeds are designedto ensure the liftoffspeed does not exceedthe tire speed rating.14aero q u arterly qtr 02 09
Exceeding Tire SpeedRating During TakeoffAirplane tires are designed to withstand a wide range of operating conditions, includingcarrying very high loads and operating at very high speeds. It is common for a jet airplanetire to carry loads as heavy as 60,000 pounds while operating at ground speeds up to235 miles per hour. To accommodate these operational conditions, each tire has specificload and speed ratings. Tires are carefully designed and tested to withstand operationup to, but not necessarily beyond, these ratings.By Ingrid Wakefield, Flight Operations Engineer; and Chris Dubuque, Service Engineer, Landing Gear SystemsIt is uncommon to exceed the load ratingof tires during normal airline operationbecause the weight and center-of-gravityposition of the airplane are well controlledand well understood. However, onoccasion the speed rating of tires can beinadvertently exceeded during takeoff.This article discusses factors that canlead to a tire speed exceedance duringtake off, provides guidance to help preventsuch tire overspeed events, and pointsout that there are no standardized industrymaintenance guidelines if an overspeedevent occurs.IntroductionBoeing is receiving an increasing numberof operator inquiries about tire speed limitsbeing exceeded during takeoff. This doesnot appear to be a new issue. Rather,advanced data acquisition tools on modernairplanes have made operators more awareof tire speed exceedance events.In most cases, the speed exceedanceis small, only a few knots. Boeing is notaware of any of these overspeed eventsresulting in thrown treads, which suggeststhat airplane tires in good condition canwithstand these small speed exceedanceswithout damage. However, it is importantto remember that at high speeds, heat isgenerated within the tire structure. ThisWWW.boe i ng.com/commercial / aeromagaz ineheat, combined with extreme centrifugalforces from high rotational speeds, createsthe potential for tread loss. Ensuring thattires are operated within their speed ratingswill help prevent possible tread losses andthe potential for airplane damage.Conditions That Can Lead toExceeding the Tire Speed RatingDuring TakeoffWhen dispatching an airplane in compliancewith the certified Airplane Flight Manual,the airplane takeoff speeds are designedto ensure that the liftoff speed does notexceed the tire speed rating. While rotationand liftoff speeds are generally expressedin knots indicated airspeed, the tire speed15
limit is the ground speed, which is usuallyexpressed in statute miles per hour. Thismeans that a tire rated at 235 miles perhour is designed for a maximum groundspeed at liftoff of 204 knots.A number of factors can lead to a tirespeed-limit exceedance during takeoff.Typically, this occurs when an airplane isdispatched at or near the tire-speed-limitweight and:nnnThe airplane rotation rate is slower thanthe Boeing-recommended rotation rate,and/orThere is a late rotation, and/orThe tailwind is higher than anticipated.Dispatch at or near the airplane’s tirespeed limit is most likely to occur duringtakeoffs from airports at high altitudes onwarm days, because these conditions tendto drive the ground speed at liftoff of theairplane closer to the tire speed limit. How ever, tire speed limits can be encounteredduring takeoff in less severe environmentalconditions, such as when scheduling animproved climb takeoff.Crosswinds can aggravate the situationby unexpectedly shifting into a tailwind,which may further increase the groundspeed at liftoff. An unexpected (and there fore unaccounted for) tailwind componentwill directly add to the ground speed at liftoff.16Recommended TakeoffProcedures for all BoeingAirplane ModelsBoeing publishes a recommended allengine normal takeoff procedure in theFlight Crew Training Manual (FCTM) for727, 737 Classic, and Next-Generation737, 747, 757, 767 and 777 models and inthe Flight Crew Operations Manual for 717,MD, and DC models. In order to avoid tirespeed-limit exceedance during takeoff,Boeing stresses adhering to the recom mended average all-engine takeoff rotationrate of 2 to 3 degrees per second, whichprovides adequate tail clearance marginswith a target liftoff attitude reached afterapproximately 3 to 4 seconds (see fig. 1).Tail clearance margins for all 7-seriesmodels except the 717 are also outlined inthe FCTM. Tail clearance and tail strikeconcerns are often the reason flight crewsgive for opting to use a slower rotation ratethan recommended by Boeing. (Moreinformation about tail strike prevention canbe found in AERO first-quarter 2007.)When dispatching at or near the tirespeed-limit weight, which is most likelyto occur at hot temperatures and highelevations, a slower rotation than theBoeing-recommended 2- to 3-degrees-persecond average may increase the actualgroundspeed at liftoff beyond the certifiedtire speed limit. In addition, a slow rotationor under-rotation could significantlyincrease the runway distance required toreach the 35-foot point, which is anotherimportant reason for adhering to theBoeing-recommended rotation procedure.Wind AccountabilityThe certified tire-speed-limit weight doesnot contain any margin for wind account ability. For instance, the FAA-certifiedtakeoff field-length-limit weight typicallycontains a conservative factor for windaccountability of 1.5 times the tailwind and0.5 times the headwind. In comparison,the tire-speed-limit weight lacks any suchconservative wind factor. Because of this,an unexpected tailwind component notaccounted for in the takeoff analysis,occur ring during a takeoff at or nearthe tire-speed-limit weight, may increase thetrue ground speed at liftoff beyond the tirespeed rating.To avoid a tire-speed-limit exceedance,Boeing recommends to conservativelyaccount for the tailwind component whendispatching at or near the tire-speed-limitweight in a crosswind situation. Generalguidelines for crosswind takeoffs are out lined in the FCTM. These guidelines includethe recommendation to use a higher thrustsetting than the minimum required in orderto minimize airplane expo sure to gustyconditions during rotation, liftoff, andinitial climb.747-400 Case StudyA case study of the 747-400 helps illustratethis point. The operator sporadicallyexceeded the tire speed limit even thoughthe takeoff analyses showed a notablebuffer between the tire-speed-limit weightaero q u arterly qtr 02 09
Figure 1: Typical rotation, all engines777-200 – 777-300ERThe recommended rotation rate of 2 to 3 degrees per second providesadequate tail clearance margins with a target liftoff attitude reached afterapproximately 3 to 4 seconds.VRLiftoffV2 1514 35 ft7–9 046.5Time (Seconds)737-300/-400/-500VR717LiftoffV2 15VRLiftoffV2 – V2 10 20 max.16–18 35 ft8–10 0306.53–45–7V2 10,not toexceed 20 Time (Seconds)Time (Seconds)737-600 – 737-900ERVR35 ft7–10 MD-80LiftoffV2 15VRLiftoffV2 – V2 10 20 max.15–16 35 ft7–9 0335 ft8 06.52.55–6V2 10,not toexceed 20 Time (Seconds)Time (Seconds)MD-90747-400VRLiftoffVRV2 10LiftoffV2 – V2 10 20 max.15 35 ft10 0406.52.5V2 10,not toexceed 20 5–7Time (Seconds)Time (Seconds)757-200 – 767-400VR35 ft8 MD-11LiftoffV2 15VRLiftoffV2 10 25 max.15 35 ft7–11 046.5Time (Seconds)WWW.boe i ng.com/commercial / aeromagaz ine35 ft7–10 03–45–7V2 10,not toexceed 25 Time (Seconds)17
Figure 2: 747 Case study summaryRelatively large weight margins did not result in corresponding speed margins.Takeoff ITakeoff IIDispatch Weight: 805,000 poundsDispatch Weight: 825,000 poundsTire-Speed-Limit Weight: 845,000 poundsTire-Speed-Limit Weight: 855,000 poundsWeight Margin: 40,000 poundsWeight Margin: 30,000 poundsScheduled Ground Speed at Liftoff: 196 knotsScheduled Ground Speed at Liftoff: 199 knotsRated Tire Speed: 204 knots (235 miles per hour)Rated Tire Speed: 204 knots (235 miles per hour)Speed Margin: 8 knotsSpeed Margin: 5 knotsFigure 3: Effect of slow or under-rotation on all-engine takeoff distanceA 747-400 taking off with a rotation rate that is 1 degree per second slower than normal canresult in a 4- to 5-knot liftoff speed increase.VRLiftoff35 ftNormal rotationVRLiftoff35 ftUp to 700 ftSlow rotation(1 deg per sec slower than normal)VRLiftoffUnder-rotation(Rotate to 5 deg less than target)1835 ftUp to 700 ftaero q u arterly qtr 02 09
and the actual dispatch weight. The airlineapproached Boeing for assistance.The study was performed at two differ ent dispatch weights: 805,000 poundsand 825,000 pounds. There was a40,000‑pound and a 30,000-pound marginbetween sched uled dispatch weight andthe tire-speed-limit weight. These weightmargins, which appear relatively large, onlyresulted in speed margins of 8 knots and5 knots between the asso ciated groundspeeds at liftoff and the tire speed rating(see fig. 2).This case study shows the relationship ofa tire-speed-weight margin to the associatedspeed margin for a four-engine airplane.Under similar dispatch conditions on atwo-engine airplane, a similarly large weightmargin can be expected to result in aneven lower speed margin, due to the higherall-engine acceleration.The same case study showed that arotation rate that is 1 degree per secondslower than normal can result in a 4- to5-knot liftoff speed increase. This is inaddition to the increase in all-enginetakeoff distance associated with theslow takeoff rotation (see fig. 3).This illustrates how a slower-thannormal rotation rate can easily use upwhat may seem like a large tire-speed-limitmargin, especially if paired with a highertailwind component than accounted for inthe takeoff analysis used for dispatch.Maintenance Actions afterExceeding the Tire Speed LimitDuring TakeoffAlthough tire-speed-limit exceedanceevents during takeoff are not a new phe nomenon, widespread recognition of theseoverspeed events is relatively new becauseof advances in flight data recorder tech nology that enables easier data acquisition.Airplane manufac turers, tire suppliers, andregulators have not yet developed anindustry-accepted set of maintenanceinstructions following a tire-speed-limitexceedance event during takeoff.One maintenance suggestion would bethat all wheel/tire assemblies be removedfrom the airplane before further flight aftersuch an event occurs. In practice, however,replacing all of the wheel/tire assemblieson an airplane represents a major logisticalproblem and likely results in flight cancel lations and/or dispatch delays. It would bedifficult to locate and ship 18 wheel/tireassemblies to a 747 at a remote locationfollowing one of these events! Additionally,if the overspeed was very small (say, 2 to3 knots over the tires’ speed limit), it isunlikely that the tires would have sufferedany damage.Some operators have elected to simplyexamine the tires after an overspeed takeoffevent using the normal tire inspection criteriain Chapter 32 of the Airplane MaintenanceManual. If no damage is found, the air planesare dispatched normally and no furthermaintenance actions are performed. Basedon many years of service experience, thisapproach seems to have worked wellbecause very few, if any, tire tread losseshave been attributed to an overspeedevent. Based on this service experience,Boeing has typically not objected to thispractice even though there is no overspeedtakeoff capability specifically designed intothe tire.If an operator has any questions aboutthe integrity of the tires, the wheel/tireassemblies should be replaced beforefurther flight.Additional information on tire mainte nance procedures can be found in theairplane maintenance manuals and inthe following documents:nnFAA Advisory Circular 20-97B, “AircraftTire Maintenance and OperationalPractices,” April 18, 2005, U.S.Department of Transportation.“Aircraft Tire Care And Maintenance,”Goodyear Aviation, 10/04, f.WWW.boe i ng.com/commercial / aeromagaz inennnnBridgestone Aircraft Tires, Tire Care,and Maintenance, http://ap.bridgestone.co.jp/pdf/Care and Maintenance.pdf.Bridgestone Aircraft Tires, Examination,and Recommended edaction.html.Aircraft Tire Care & Service Manual,Michelin, www.airmichelin.com/pdfs/Care and Service manual.pdf.General practices manual for aircrafttyres and tubes, Dunlop Aircraft TyresLimited, 01/08, www.dunlopaircrafttyres.com/tech support/dm1172/DM1172.pdf.SummaryAlthough it is uncommon to exceed theload rating of tires during normal airlineopera tion, Boeing is receiving an increasingnumber of operator inquiries about tirespeed limits being exceeded during takeoff.There is no industry consensus on themaintenance actions that should be takenfollowing tire-speed-limit exceedanceduring takeoff. At this time, operators, inconjunction with their regulatory agency,must determine the most appropriatemaintenance action based on the tirespeed-limit exceedance event.The best approach is to try to avoidoverspeed takeoffs altogether. By takingthe following steps, flight operationspersonnel can reduce the possibility of tirespeed-limit exceedance during takeoff:nnnFollow the Boeing-recommendedrotation procedure.When dispatching at or near the tirespeed-limit weight in a crosswindsituation, consider conservatively,accounting for the tailwind component.When dispatching at or near the tirespeed limit in gusty wind and strongcrosswind conditions, use a higher thrustsetting than the minimum required.For more information, contact BoeingFlight Operations Engineering at flightops.engineering@boeing.com.19
Flight Crew Training Manual (FCTM) for 727, 737 Classic, and Next-Generation 737, 747, 757, 767 and 777 models and in the Flight Crew Operations Manual for 717, MD, and DC models. in order to avoid tire-speed-limit exceedance during takeoff, Boeing stresses adhering to the recom-mended average all-engine takeoff rotation
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CAP – Cessna Short- and Soft-Field Operations 1 February 2017 . ACS – Short-Field Takeoff Standards . Review ACS Short Field Takeoff standards.\爀屲Takeoffs and climbs from fields where the takeoff area is short or the available t\ൡkeoff area is restricted by obstructions require that the pilot operate the airplane at the limit of its takeoff performance ca對pabilities.
Figure 2. MMS Tutorial main menu Figure 3. Takeoff module screen 4.2. Requisition Module Once the takeoff data is stored in the takeoff file, the user can use the requisition screen (Figure 5) to consolidate takeoff data and generate a requisition. For example, assume there is 200 ft of 2 inch pipe on drawing
V-Speeds C172-SP 4 Normal and Crosswind Takeoff and Climb 5 Soft Field Takeoff and Climb 8 . Airspeed Indicator is Increasing AIRSPEED ALIVE Airspeed Reaches V R ROTATE Positive Rate of Climb After Takeoff POSITIVE RATE 1,000 Feet From Assigned Altitude 1,000 FEET
V SPEEDS Multi‐Engine airplanes use the same "V"‐speeds as single‐engine airplanes. However, multi‐engine airplanes have additional V‐speeds and airspeed indicator markings relating to one engine inoperative flight. Unless otherwise noted, V‐speeds given in the AFM/POH/IM apply to sea level
whenever any PDF file that is rendered using Adobe Acrobat. This tutorial demonstrates a complete takeoff using a multipage PDF (Vector) file. Towards the end of the tutorial, importing objects from a DWG CAD vector file are also covered. Now let’s get started D. Project Tab Start the takeoff at the Project tab. Here the project is defined.
36-2 ePlan Takeoff Tutorial--Residential ePlan Takeoff Tutorial—Residential A RoofLogic Digitizer license upgrades RoofCAD so that you have the ability to digitize paper plans, electronic plans and satellite images. This tutorial is an introduction to how to digitize an ePlan (electronic plan).
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