Editing Lockheed L-1011 TriStar (section)

==Design==
[[File:EGVN - Lockheed L-1011 Tristar K1 - Royal Air Force - ZD948 (40205452283).jpg|thumb|Lockheed L-1011 TriStar front view]]

=== Engines ===
The [[Rolls-Royce RB211|RB211]] and its features, despite the delays in its development, provided the L-1011 with then-unmatched fuel economy and noise levels.<ref name=":0">{{Cite book|last=Upton, Jim.|url=https://www.worldcat.org/oclc/48491576|title=Lockheed L-1011 Tristar|date=2001|publisher=Specialty Press Publishers and Wholesalers|isbn=1-58007-037-X|location=North Branch, MN|oclc=48491576}}</ref>{{Rp|23}}

==== Reversers and nozzle ====
During development the RB211 engines on the L-1011 had ''thrust-spoilers'' – [[Target-type thrust reversal|target-type]] hot-stream reverse buckets – alongside the cold-bypass reversers. Despite capturing 25% of the total engine thrust, aerodynamic interference with the flaps diminished the braking effect of the flaps, so the thrust-spoilers were removed; instead an 11-degree afterbody was installed, which improved the specific range by 1.5%. Further improvements led to a 15-degree afterbody, enabling the L-1011 "to beat its predicted specific air range at 0.85 Mach by between 3.5 and 5.5 percent, the exact figure depending on cruise weight."<ref name=":0" />{{Rp|26–27}}

=== All-flying tail ===
Instead of the [[Stabilizer (aeronautics)#Horizontal stabilizer configurations|trimmable horizontal stabilizer]] (THS) found on most jetliners of its time, the L-1011 incorporated an all-flying tail – a [[stabilator]]. The aft portion had a geared (anti-[[Servo tab|servo]]) [[Elevator (aeronautics)|elevator]] that was linked to and moved with the stabilator, changing the stabilator's camber and improving the overall control surface effectiveness. Lockheed's main drive away from a THS was "[eliminating] mis-trim and runaway trim problems that have contributed to a number of accidents in the past."<ref name=":0" />{{Rp|30–31}}<ref>{{Cite book|last=Beach|first=J. B.|title=SAE Technical Paper Series|date=1968-02-01|chapter=Designing the Lockheed L-1011 to Meet Airline Needs Beyond 1970|volume=1|chapter-url=https://www.sae.org/publications/technical-papers/content/680545/|language=en|location=Warrendale, PA|pages=2229|doi=10.4271/680545}}</ref> The fact that the elevators are not moved directly led to the failure in recognizing the jamming (trailing edge up) of the left elevator aboard [[Delta Air Lines Flight 1080]] in 1977.<ref>{{Cite web|last=LisbonJet|first=Publicada por|title=Delta flight 1080 incident|url=https://blog.tristar500.net/2017/08/delta-flight-1080-incident.html|access-date=2020-12-10|language=en}}</ref>

=== Fuel system ===
The L-1011-1 has four wing tanks; each inboard tank feeds the respective wing engine, and the two outboard tanks feed the tail engine via a flow equalizer.<ref name=":0" />{{Rp|33}} The additional center tank of the long-range variants, which is two halves, is located between the wing halves. Each center tank half acts as additional capacity to its adjacent inboard wing tank; filling it by way of [[Injector|ejector pumps]]. When the center tank is filled, it is used to [[Aircraft fuel system#Multi-engine aircraft fuel system|crossfeed]] all three engines in flight (by way of the ejector pumps and crossfeed valves) until the center tank is empty and the remaining tanks are equalized.<ref>{{Cite book|url=https://apps.dtic.mil/dtic/tr/fulltext/u2/a119572.pdf|archive-url=https://web.archive.org/web/20200321124424/https://apps.dtic.mil/dtic/tr/fulltext/u2/a119572.pdf|url-status=live|archive-date=March 21, 2020|title=Commercial Aircraft Airframe Fuel Systems Survey and Analysis|publisher=FAA Technical Center|year=1982|pages=41–44}}</ref>

[[File:TWA Lockheed L-1011 Tristar coach cabin.jpg|thumb|Coach cabin of a [[TWA]] L-1011 TriStar in 2–5–2 layout]]

=== Landing gear ===
The nose landing gear had two attachment points forward and aft, allowing a short-enough [[Pushback (aviation)|tug]] to push or pull the plane from directly underneath, a feature to allow operations where there wasn't enough forward space at some airports, which was more common at the time.<ref name=":0" />{{Rp|34}}

=== Electrical system and avionics ===
[[File:Lockheed L-1011 Tristar simulator cockpit RAF museum.jpg|thumb|The L-1011 TriStar's three-crew flight deck]]
The L-1011 was the first jetliner to have an [[integrated drive generator]] (IDG).<ref name=":0" />{{Rp|34}}

The FMS on the L-1011, certified by the FAA in September 1977, offered many features that have since become common. The features were aimed at greatly reducing crew workload and improving [[fuel efficiency]]. Of those are a Mach/IAS cruise control, an automatic Rough Air Mode that detects turbulence and adjusts the engine power setting accordingly, and a descent mode that figures out the optimum location to start a descent by "back computing" from a preselected point, allowing "on-altitude and on-speed" arrival.<ref name=":0" />{{Rp|36–38}}

The L-1011 also featured a highly advanced [[autopilot]] system and was the first widebody to receive [[FAA]] certification for [[Instrument Landing System#ILS categories|Cat-IIIc]] [[autoland]]ing, which approved the TriStar for completely [[instrument meteorological conditions|blind]] landings performed by the aircraft's autopilot in zero-[[visibility]] weather.<ref>{{cite news |last= Young |first= David |url= https://pqasb.pqarchiver.com/chicagotribune/access/614749782.html?dids=614749782:614749782&FMT=ABS&FMTS=ABS:AI&type=historic&date=Sep+18%2C+1977&author=&pub=Chicago+Tribune&desc=Look+Ma%2C+no+hands--learning+how+to+land+a+jumbo+jet&pqatl=google |title= Look Ma, no hands—learning how to land a jumbo jet |work= Chicago Tribune |date= September 18, 1977 |access-date= July 6, 2017 |archive-date= November 5, 2012 |archive-url= https://web.archive.org/web/20121105083907/http://pqasb.pqarchiver.com/chicagotribune/access/614749782.html?dids=614749782:614749782&FMT=ABS&FMTS=ABS:AI&type=historic&date=Sep+18,+1977&author=&pub=Chicago+Tribune&desc=Look+Ma,+no+hands--learning+how+to+land+a+jumbo+jet&pqatl=google |url-status= dead }}</ref> The L-1011 used an inertial navigation system to navigate;<ref>{{cite web |url= http://www.es.northropgrumman.com/solutions/ltn92/assets/LTN-92_Ring_Laser_Gyro_Inertia.pdf |title= LTN-92 Laser Gyro INS |archive-url= https://web.archive.org/web/20110927145118/http://www.es.northropgrumman.com/solutions/ltn92/assets/LTN-92_Ring_Laser_Gyro_Inertia.pdf |archive-date= September 27, 2011 |publisher= Northrop Grumman |access-date= July 16, 2011}}</ref><ref>{{cite book |url= http://www.tristar500.net/articles/cstmp_stansted.pdf |title= Report: Lockheed L1011-500 Tristar, CS-TMP |archive-url= https://web.archive.org/web/20091222142615/http://www.tristar500.net/articles/cstmp_stansted.pdf |archive-date= December 22, 2009 |publisher= Air Accidents Investigation Branch |access-date= July 16, 2011}}</ref> this included aligning the navigation system by entering current coordinates of longitude and latitude.<ref name="ReferenceA" />

It also had a unique direct lift control (DLC) system, which allowed for smooth approaches when landing, without having to use significant pitch changes while on the approach path.<ref>{{cite report |url= http://www.aaib.gov.uk/cms_resources.cfm?file=/dft_avsafety_pdf_501051.pdf |title= Report: Lockheed L1011-385-1-14, G-BBAF |page= 5 |publisher= Air Accidents Investigation Branch |access-date= July 16, 2011}}</ref><ref>{{cite magazine |last= Kocivar |first= Ben |url= https://books.google.com/books?id=-AAAAAAAMBAJ&q=l1011&pg=PA50 |title= Giant Tri-Jets Are Coming |magazine= Popular Science |volume= 197 |issue= 6 |date= December 1970 |pages= 50–52 |issn= 0161-7370}}</ref> DLC helps maintain the aircraft on the glideslope during final approach by automatically deploying spoiler panels on the wings. Thus, rather than maintaining the descent by adjusting pitch, DLC helps control the descent while maintaining a more consistent pitch angle, using four redundant hydraulic systems.

=== Other components and systems ===
The APU, which was the Pratt and Whitney [[Pratt & Whitney Canada PT6|ST6L]],<ref>{{Cite web |title=ST6L-73 Tristar Auxiliary Power Unit |url=https://gasturbineworld.co.uk/tristar-aircraft-apu/ |access-date=2025-01-31 |website=gas turbine world |language=en-US}}</ref> was capable of operating up to 30,000 feet; its two square-shaped inlet doors are situated on the bottom fuselage on the aircraft's centerline towards the rear of the plane.<ref name=":0" />{{Rp|28}}

Compared to the typical three-system of its era, the L-1011 had four independent 3,000-psi hydraulic systems, A through D.<ref name=":0" />{{Rp|29}}

Part of the production process also used a unique [[autoclave]] system for bonding fuselage panels together; this made the L-1011 extremely resistant to corrosion.