YAK 141

[SUBS17]

YAK141 and the F35B both have a similar configuration, I think it would be good for the YAK141 to have a 4 Directional TVN like the F35B.

[F-2]

Quote

A great deal of misinformation has appeared on the Internet regarding the relationship of the Soviet Yak-41 (later Yak-141), NATO reporting name Freestyle, to the X-35 and the rest of the JSF program. The Pratt & Whitney 3BSD nozzle design predates the Russian work. In fact the 3BSD was tested with a real engine almost twenty years before the first flight of the Yak.

Throughout the 1970s and 1980s, the Soviet Navy wanted a supersonic STOVL fighter to operate from its ski jump equipped carriers. At what point the Yakovlev Design Bureau became aware of the multi-swivel nozzle design is not known, but the Soyuz engine company created its own variant of it. The Yak-41 version of the nozzle, from published pictures, appears to be a three-bearing swivel duct with a significant offset “kink.” The Yak-141 also used two RKBM RD-41 lift engines – an almost identical arrangement to the Convair Model 200 design. The aircraft was also re-labeled as a Yak-141 to imply a production version, but no order for follow-on series came from the Russian Navy.

The Yak-141 was flown at the Paris Airshow in 1991. The flight displays of the Yak were suspended when the heat from the lift engines started to dislodge asphalt from the tarmac. At the 1992 Farnborough show, the Yak was limited to conventional takeoffs and landings with hovers performed 500 feet above the runway to avoid a repeat performance of asphalt damage. But the Yak-141 does deserve credit for being the first jet fighter to fly with a three-bearing swivel nozzle – twenty-five years after it was first designed in the United States.

During the early days of the JAST effort, Lockheed (accompanied by US government officials from the JAST program office) visited the Yakovlev Design Bureau along with several other suppliers of aviation equipment (notably also the Zvezda K-36 ejection seat) to examine the Yakovlev technologies and designs.

Yakovlev was looking for money to keep its VTOL program alive, not having received any orders for a production version of the Yak-141. Lockheed provided a small amount of funding in return for obtaining performance data and limited design data on the Yak-141. US government personnel were allowed to examine the aircraft. However, the 3BSN design was already in place on the X-35 before these visits.

https://www.codeonemagazine.com/f35_article.html?item_id=137

If anyone wants to send an FOIA request to the F-35 system program office or has friends at Lockheed, get us that data package!

[SUBS17]

The F35A/B/C and YAK141 would be good addons for DCS.

[MiG21bisFishbedL]

Someone tried with the former some time ago and it amounted to nothing. As nifty as they are, it's just not feasible.

Edited January 3, 2022 by MiG21bisFishbedL
Confused former and latter, I am smart.

[F-2]

Quote

ASSESSMENT OF RUSSIAN VSTOL TECHNOLOGY EVALUATING THE YAK-38 "FORGER" AND YAK- 141 "FREESTYLE" A. Nalls USMC, USA M. W.Stortz NASA Ames Research Center, Moffett Field, California, USA BACKGROUND The dissolution of the Former Soviet Union (FSU) created new relationships between the world superpowers. Overnight, the Com¬ monwealth of Independent States (CIS), formed from the remnants of the FSU, began the difficult transformation to a free market society. Indirectly, one of the world's supreme arsenals became virtual surplus. The chief military customer, the Soviet government, no longer existed and the smaller states could not afford expensive hardware. This shift in philosophy halted major development programs, suspended pro¬ duction lines and forced the design bureaus, now independent "companies" to explore new commercial markets. The design bureaus were no longer subsidized and now forced to deal with the western problems of competition, profit motive and cash flow. Military hardware that had once been highly classified and the basis for our own defense planning, was now openly marketed at air- shows around the world. "Test" flights were available for potential cus¬ tomers and cooperative partnerships were explored between former adversaries. Almost anything and everything could now he bought outright, including much of the FSU's premier achievements of tech¬ nology. In many respects, it was a buyer's market. This environment permitted a visit to the Yakovlev Design Bu¬ reau, (Yak) for a VSTOL technology assessment. Yakovlev is the FSU's sole Design Bureau with experience in VSTOL aircraft and has developed two flying examples, the Yak-38 "FORGER" and Yak-141 "FREESTYLE". This visit was the first time that westerners were per¬ mitted such candid insight into these two previously classified aircraft. The Yak-38 FORGER became operational around 1975 aboard the carrier KIEV, and is chronologically equivalent to the western AV -8A "HAR.RIER." However, FORGER is markedly different from HARRIER and utilizes different technology for flight controls and vertical lift. FORGER has two lift engines, used only for vertical flight, embedded 47J SEcnjon 4 in the forward fuselage and a single lift/cruise engine in the aft fuselage for both vertical and wingborne flight. This multi-engine configuration is dubbed Lift plus Lift/Cruise (LLC). The FORGER, built exclusively for shipboard operation, was originally designed as Vertical Takeoff/Vertical Landing (VTOL) only, but developed a Short Takeoff (STO) mode in response to western criticism of limited capability. The Yak-141 FREESTYLE is a research and development testbed, designed to succeed FORGER with major advancements in flight con¬ trols and performance. It builds on the experience of the Yak-38 and uses a nearly identical LLC configuration with a much larger cruise engine providing a flying supersonic VSTOL aircraft. After its first flights in 1988, FREESTYLE claimed 12 world records for VSTOL air¬ craft, previously held by HARRIER. Additionally, this aircraft has many features highly integrated into the flight control system to simplify the pilot tasks and reduce workload, especially during VSTOL flight. FREESTYLE and FORGER were displayed at the Farnborough Airshow 92 and there Art Nalls contacted representatives from the Yakovlev Design Bureau about a visit to study the two aircraft. The initial contact was quite successful, resulting in a complete detailed tour of the aircraft on the flight line including a cockpit orientation. More detailed discussions were held later in the United States and re¬ sulted in an official invitation from Mr. Alexancder Dundukov, Chair¬ man and Chief Designer of Yakovlev, for a Navy/NASA team to visit Russia. This initial visit also included familiarization flights in the Yak -38U, two-seat FORGER. These flights were the first time western test pilots would be permitted in any Russian VSTOL aircraft. DESCRIPTION Yak-38 FORGER The Yak- 38 is a 3-engine, subsonic, maritime combat aircraft. It has a shoulder-mounted, modestly-swept, low aspect ratio, heavily loaded wing. Two 7800 lb thrust Rybinsk RD-36 dedicated lift engines are mounted in tandem behind the Cockpit and inclined forward 10 degrees. The 18,000 lb thrust Tumansky R-27 main engine flow exits through two low, side mounted, swiveling nozzles with a vectoring range of 90 degrees. A bifurcated inlet with a semi-circular cross-sec¬ tion has a single row of auxiliary inlet doors very similar to HARRIER. Other notable external features include the lift engine inlet and exit doors on the upper and lower fuselage, a flow blocker dam to protect the main inlet from reingestion, ventral strakes to trap the jet fountain and dorsal strakes to separate the jet fountain from the fuselage and protect the lift engines from reingestion. Additionally, the aircraft has 474 SECTION 4 a wing fold capability for shipboard operations and a drag chute used for conventional landings (see fig. 1). The flight control system is conventional hydromechanical in the lateral and directional axes and fly-by-wire in the longitudinal axis. It is a triplex, analog system that fully integrates the flight and propulsion systems. The single throttle lever controls the overall thrust level of all three engines in VSTOL flight and a bi-directional, spring-centered switch mounted on the otherwise conventional stick provides thrust vector control. Pitch re¬ sponse type is rate command in conventional flight and converts to attitude command, attitude hold (ACAH) in VSTOL flight. A bleed air reaction control system (RCS) provides lateral and directional attitude stabilization and control as the conventional surfaces lose their aero¬ dynamic effectiveness in VSTOL flight. Differential thrust between the lift engines and the lift/cruise engine is used for maneuvering control and pitch trim in the presence of total thrust modulation and thrust vector deflection. It is remarkable that this fully integrated flight and propulsion system was developed in the early 70's and operational in 1975. The cockpit is quite roomy but lacks a built-in ingress/egress system. The canopy is hinged on the starboard side and manually op¬ erated. The cockpit field of view (FOV) in the two seat trainer is somewhat limited downward laterally at the canopy sill, which comes to shoulder level (see fig. 2), and aft by the ejection seat head rest. The lateral FOV in the single seat version is better. The KA-36, the Russian standard for ejection seats, is modified with a VSTOL variant and has automatic initiation in VSTOL flight, based on a combination of attitude and attitude rate for both pitch and roll. Automatice initia¬ tion of ejection is a concepte completely new to the western world and unique to the Yakovlev VSTOL aircraft. The general layout of the in¬ strument panel is similar to the first generation HARRIER with the engine instruments on the right and flight instruments on the left. Of course, the labeling is in Russian Cyrillic and the units are metric. No¬ table features include a prominently displayed nozzle angle gage, dual tape lift engine RPM indicators, combination alpha and g-meter, combination VSI and turn-and-slip indicator, and numerous indicator, caution and warning lights. A vertical row of 7 advisory lights on the right hand side of the instrument panel advise of the systems neces¬ sary for vertical flight. All seven lights should be illuminated under normal operating conditions for vertical operations. A HUD is con¬ spicuously absent, fig. 3 contains a more complete description and lo¬ cation of the instruments. The left console contains the throttle quadrant and all other sys¬ tem switches (see fig. 4). The throttle has a rather short throw of ap¬ proximately 5 inches at the throttle grip and lacks an arm rest to assist with precise throttle inputs. The 3-position lift engine start lever (OFF, STOL, VERTICAL) is located inboard of the throttle and has a large, square knob with' a lock mechanism which provides unmistakable 475 SECISJOn 4 tactile cueing. The right console contains the usual communications and navigation equipment and is otherwise unremarkable. The center control stick and rudder pedals are conventional ex¬ cept that a hand-actuated brake lever is provided on the forward side of the control stick rather than toe-operated brakes on the rudder pedals. Steering is accomplished through differential braking which is commanded by a combination of pedal deflection and brake lever application. The main engine nozzle angle is controlled through a bi¬ directional switch on the center stick that commands the main engine nozzles at a constant rate in the commanded direction. Aft actuation lowers the nozzles from horizontal, forward actuation moves the noz¬ zles back to the horizontal conventional thrust position. To condition the propulsion system for VSTOL flight, the lift engine start lever is positioned to either STOL or VERTICAL. This automatically opens the lift engine inlet, located on the upper fuselage behind the cockpit, the lower exhaust doors on the fuselage belly, and starts the lift engines. Lift engines are started with main engine bleed air on the ground and airborne, but will automatically air start airborne, if the bleed air sys¬ tem fails. When the lift engines are started, the flight control system automatically shifts to ACAH mode. Lift engine thrust is scheduled by the flight control computers as a function or airspeed, main engine nozzle angle and throttle position. As noted above, lift engine and main engine thrust are differentially regulated for pitch balance and at thrust vector angles greater than 60 degrees (measured from the hori¬ zontal) the total thrust is regulated to hold the total vertical compo¬ nent constant. The result is an aircraft with very pleasant handling characteristics in VSTOL flight. For a STO, the nozzle angle is initially set at 30 degrees (with re¬ spect to the waterline) and the lift engine thrust is just above idle (point A, fig. 5). Wlren full throttle is selected to begin the takeoff roll, the lift engine thrust is increased to the maximum corresponding to the 30 degree nozzle deflection (point B, fig. 5). At the proper speed, based on measured longitudinal acceleration and ambient tem¬ perature, the flight control computers automatically increase the noz¬ zle deflection to 60 degrees and the lift engine thrust to maximum (point C, fig. 5) and the aircraft becomes airborne. As the aircraft ac¬ celerates through a speed of 250 km/hr (135 kts) the pilot adjusts the nozzle angle to 45 degrees and holds it there until a speed of 300 km/hr (162 kts). After that, the nozzles are adjusted aft and the lift engines are shut down manually. Lift engine operation is limited to 3 minutes for cooling considerations. Yak-141 FREESTYLE The Yak-14i is a prototype, supersonic, carrier-based fighter in¬ tended to replace the Yak-38 (see fig. 6). Aircraft development is cur- 476 SECTION 4 rently suspended, due to lack of funding and commitment by the mili¬ tary. The propulsion concept and control scheme are similar to the Yak-38, but several of the pilot functions are more highly automated and refined and a much larger cruise engine provides a supersonic dash capability. The shoulder-mounted wing is moderately swept and highly loaded (greater than 120 lbs per sq. ft at projected combat weight). Twin vertical tails are boom mounted and straddle the main engine nozzle. The fixed inlet is bifurcated with initially rectangular cross-section and auxiliary inlet doors on the upper and side surfaces. Lift engine inlet and exit doors are mounted and operate in the same fashion as on the predecessor. A forward flow, dam is located aft of the lift engine exit to trap the Jet fountain and minimize reingestion. Side- mounted strakes, a wing root leading edge extension and the sharp upper corner of the main engine inlet serve to separate the jet foun¬ tain from the fuselage and protect the lift engines from reingestion. The main engine, designated R-79 and of the 35,000 lb thrust class, was developed by the Soyuz Design Bureau and incorporates a single vectoring nozzle that permits afterburner operation at any thrust angle. Significant attention was paid to stability of operation during rapid thrust changes as RPM and afterburner fuel flow are modulated simultaneously in VSTOL flight. Thrust vectoring is ac¬ complished by means of two counter-rotating "stove pipe" sections be¬ tween the core and afterburner and the vectoring range is from -10 degrees to 95 degrees with respect to the aircraft waterline (see fig. 7). The rotating nozzle is convergent only and when rotated down is very close to the landing surface, creating a very harsh ground envi¬ ronment. Surface requirements are reported no more stringent than for the non-afterburning Yak-38 which requires either a tile or steel sur¬ face, however very little testing has been done in this regime. The Rybinsk Design Bureau was responsible for the two 9200 lb thrust RD-41 lift engines, which were adapted from a conventional, horizontally mounted engine. Modifications to convert the engines to vertical lift and minimize weight included the elimination of the high pressure fuel pump (high pres.sure fuel is supplied by the main engi¬ ne, replacement of the closed-loop lubrication system with a light weight, sacrificial oil injection system, replacement of the mechanical starter with a bleed air impingement start system and installation of the nozzle system with vectoring capability of ±12.5 degrees. The combination of the vectoring capability and the installation angle of 10 degrees forward provides a total vectoring range of 2.5 degrees forward to 22.5 degrees aft, as measured from the vertical (see fig. 8). The flight control system is nearly identical to the Yak-38, except for improvements to automate STO functions and reduce pilot workload. It remains a triplex, analog, FBW in the longitudinal axis, and hydromechanical in the lateral and directional axes, although a digital system was reported to have been in development. As before, all engines are integrated into a single throttle and the thrust vector 477 SEcruon 4 angle of the main engine is controlled through a thumb actuated switch on the control stick, similar to the Yak-38. A schematic of the longitudinal flight and propulsion control system is presented in fig. 9. The only mechanical link in the entire system is the throttle to main engine and it is used for backup. The response type is similarly ACAH in VSTOL flight using differential engine thrust for pitch control and trim. A bleed air RCS provides control in the lateral and directional axes. The first aircraft had a tail boom ejector RCS for directional control, which was detailed in "Aviation Week." However, directional control was reportedly poor and the second flying prototype was improved with a nose-mounted RCS which provided greater control power through a longer moment arm. The cockpit of the Yak-141 is similar to the Yak-38 in many re¬ spects. It is equally roomy with a starboard hinged, manually operated canopy and the KA-36 ejection seat headrest remains an obstruction to rear FOV, although the lateral FOV is improved through a lower can¬ opy sill. The general layout of the instrument panel is the same and consists of all round gages. Reportedly, the instrument panel was bor¬ rowed "off the shelf" from a MiG-29 to save prototyping costs for the first flying model, with plans for a modernized "glass cockpit" for the second and subsequent models. Warning, caution and status lights are quite numerous, with nearly 50 lights scattered throughout the main panel. A HUD was planned for the aircraft, but in its place is a large panel with a flight test airspeed indicator and a small array of indica¬ tor lights, likely associated with test instrumentation. The instrument panel and the location of the instruments is presented in fig. 10. On the left console, the throttle has been raised and operates in linear fashion on a rail mounted on the cockpit sidewall. Total throw is approximately 10 inches, with the last 2 inches dedicated for after¬ burner modulation. A small gate must be passed to select afterburner and must be intentionally de-selected to prevent inadvertent canceling of afterburner during critical VSTOL operations. This was reportedly the cause of the second prototype sustaining a very hard shipboard landing, resulting in strike damage and an automatic ejection of the pilot. The VSTOL selector knob is again located inboard of the throttle and operates in the same manner described for the Yak-38 (see fig. 11). The usual communication and navigation equipment is mounted on the right console. The control stick and rudder pedals are conventional as noted for the Yak-38 and nozzle angle is commanded by a similar bi-directional switch on the stick. Hand lever operated wheel braking is retained but nosewheel steering through the rudder pedals is added and invoked through an additional button on the stick. A flight control "recoveiy'^" mode is provided whereby the aircraft recovers to straight-and-level flight and is summoned via a panic but¬ ton on the stick. The propulsion system is configured for VSTOL in the same manner and the lift engine start sequence is identical to the Yak-38. 478 SECT/On 4 For vertical flight the two lift engine nozzles are toed-in to prevent a jet fountain forming between them and causing hot gas ingestion of the lift engine cavity. Lift engine thrust is scheduled as described above and pitch is controlled through differential thrust but since the main engine is operated in afterburner for VSTOL flight, the ground environment is extremely harsh. The STO is accomplished in like manner to the Yak-38 through liftoff, however in addition to the manual accelerating mode, the flight control system can automatically control the main engine nozzle to achieve an optimum accelerating transition. In this automatic transition, nozzle angle is reduced in in¬ crements, of approximately 10 degrees, and aircraft airspeed and alti¬ tude referenced by the flight control computer to prevent a settle. Al¬ though supersonic performance is achieved and good handling quali¬ ties are retained, the landing environment is extremely hostile, due to the afterburner, and is a major deficiency. FLIGHT PROFILE The flights of the Yak-38U two seat aircraft were conducted at the Zhukovsky Flight Test Center from the Ramenskoye airfield. Zhu¬ kovsky, a community of approximately 100,000 people located ap¬ proximately 20 miles southeast of Moscow, is the center for Russian aerospace research and development, major facilities include the Cen¬ tral Aero-Hydrodynamic Institute (TsAGI), the Gromov Flight Research Institute (LII), the test pilot school which is currently closed, and the test bases of the various aircraft design bureaus. The first flight was flown the morning of 30 June by Art Nalls and Viktor Zabolotsky, the Chief pilot at LII. After a short turnaround of less than 30 minutes, Mike Stortz and Yuri Mitikov, the Yakovlev Design Bureau test pilot, completed a similar flight profile. The profile was chosen by the Russians and consisted of a conventional takeoff, a decelerating transition to a hover, followed by an accelerating transi¬ tion to conventional flight and limited wingborne maneuvering flight. Recovery was accomplished via straight-in to a conventional landing. Vertical landings were precluded by a reported lack of a prepared, metal landing surface. The entire flight profile was approximately 30 minutes in each case. The weather was fine with broken clouds at 15 — 2500m (5 — 8k ft) and 25 — 5000m (8 — 16k ft). The temperature was 20 deg Celsius (68 deg F) with light winds and unrestricted visibility. START/TAXI The aircraft was started by the front seat pilot and with a minimum of post start checks was ready for taxi in under 2 minutes. Taxi is straight forward and ground handling is surprisingly simple with the stick mounted brake lever and differential brakes. Despite a lack of nose wheel steering, tight turns were easily accommodated. 479 SECMON 4 although nose wheel steering would certainly be desirable for shipboard operations. TAKEOFF Maximum RPM for takeoff was 98/98% representing fan and core speeds. RPM appear to be matched above approximately 95%. Rotation was at 300 km/hr (162 kts) and unstick occurred at 350 km/hr (189kts). Takeoff roll took 17 seconds and was estimated at 3000 feet, as no runway markers were available. Gear and flap retraction was smooth and quick. Shortly after takeoff we were briefly permitted some very limited maneuvering before returning for a hover. First impressions of the aircraft highlighted a lack of control harmony. The aircraft was very heavy in pitch, requiring an estimated 20 lbs for a 3 — 4 g turn. Yaw control was also very heavy and the aircraft appeared directionally loose, yet very responsive in roll. After only a few minutes, the demonstration pilot Look aircraft control and returned to the reciprocal of the takeoff heading and positioned for a decelerating transition. DECELERATING TRANSITION AND HOVER At 600 km/hr (324 kts) and at about 3 nm straight in the landing gear were lowered, followed by starting the lift engines at 450 km/hr (243 kts) by moving the yellow cockpit lever to VERTICAL. Lift engine start is completely automatic, from opening the inlet and exit doors, starting engines,and reconfiguring the flight controls to ACAH laws. Pitch is surprisingly stable, with no tendency to "bobble" with the additional lift from the lift engines. Drag from the inlet doors is significant and unmistakable. At approximately 1.5 miles from the hover position, and still on a slight glideslope, the nozzles were lowered via the stick control switch. Deceleration was comparable to the AV-8A in a Rat attitude and attitude was held constant throughout the transition. A slight flare brought the aircraft to a stabilized hover. In the hover, mild maneuvering was permitted in pitch, roll, yaw, and altitude. A stabilized hover was easily controlled. Pitch response was sluggish, but reasonable since pitch is controlled with differential engine thrust. Pitch is so stable that minor hover adjustments fore and aft, normally made with pitch in the HARRIER, were ineffective in FORGER and perhaps could be better performed with small nozzle nudges. Roll control, with RCS, is responsive and predictable, however yaw control is sluggish, underpowered and the major deficiency of hover control, although reportedly improved . in later models. Surprisingly, height control with a single throttle controlling 3 engines was smooth and responsive. Overall, the aircraft felt smooth and stable in hovering flight with very low workload. 480 SECTION 4 ACCELERATING TRANSITION Since the lift engines are limited to three minutes of operation, we ended the hover with a 180 degree turn and initiated an accelerating transition on the original runway heading. The transition was accomplished in increments. The lift/ cruise engine nozzle was moved to 25 degrees (measured from the vertical) and held there until 250 km/hr (135 kts), then moved to 45 degrees until 300 km/hr (162 kts) was achieved. The change from 45 degrees to horizontal was made without further airspeed restriction. The lift engines were secured via the cockpit VSTOL lever and with gear and flap retraction the aircraft was configured for conventional flight. The entire transition took approximately 30 seconds. MANEUVERING FLIGHT Recommended maneuvering airspeed was 700 km/hr (405 kts), with an maximum airframe limit of 900 km/hr (486 kts). Several wingovers were performed, letting airspeed drop to as low as 300 km/hr or less over the top and controls remain effective in all axes through at least this range with no sideslip buildup. Accelerated stall warning is light to moderate airframe buffet around 4 — 5 g’s (the rear cockpit g meter was inoperative) developing into mild wingrock as the stall progresses. Recoveries are instantaneous with relaxation of backstick. N2 1-g stalls were performed. Roll performance is very good, exceeding 300 degrees per second, although adverse yaw is very evident. Roll attitude capture requires a large opposite stick "check", but is overall satisfactory. LANDING At the completion of the maneuvering phase, a conventional landing was made from a straight in approach. Landing gear was lowered at 600 km/hr (324 kts) with the flaps following at 500 km/hr (270 kts). A long, shallow approach was performed with a reference airspeed on final of 350 km/hr (189 kts). The aircraft appeared to be quite loose about all axes and large, frequent stick inputs were required to maintain course and glideslope. Speed stability was good, as few throttle inputs were required to maintain speed. Crossing the threshold, the throttle was retarded to idle and a gentle flare to landing at approximately 300 km/hr (162 kts) was accomplished. Stick activity increased markedly during the flare, requiring frequent, nearly continuous large (near full) stick deflections. Touchdown was positive, but there was some "lurching" and roll control inputs were required to maintain wings level during the initial part of ground roll. The drag chute was deployed at approximately 275 km/hr (149 kts) and the deceleration was very effective. Wheel brakes were applied without 481 SEcnion 4 limitation below 200 km/hr (108 kts) although there was no mention of an anti-skid system. TAXI, SHUTDOWN, POSTFLIGHT Taxiing with Differential brakes was again quite easily accomplished, in spite of a hairpin turn into the staging area. Large power increases were required to keep the aircraft rolling during the turns. The aircraft was secured almost immediately after arriving in the chocks and cockpit postflight appeared minimal. GENERAL IMPRESSIONS AND CONCLUSIONS The handling qualities of the Yak-38U in VSTOL flight are excellent - low workload because of the attitude hold response type and high precision because of the superb integration of the flight and propulsion systems. Maneuvering performance was only adequate and wingborne handling qualities leave a lot to be desired. The integration of the flight and propulsion systems for the Yak 38 was ahead of its time. The concept of lift thrust scheduling as a function of airspeed, lift/cruise nozzle and throttle is elegant in its simplicity. For its vintage (mid 1970's) analog, fly by-wire system of integrated flight and propulsion controls is a remarkable accomplishment. Credit is owed to the Russians for their ingenuity and persistence in making this complex system operational with such docile manners. At the risk of oversimplification, the Russian design philosophy with respect to VSTOL flight appears to be a solution basked on brut force with only minor refinements in the development process. Short takeoff procedures were developed to minimize the ground environment problem but no consideration has been given to alternate propulsion configurations. In the spectrum of powered lift configurations, the Yakovlev aircraft provide valuable information on dedicated lift systems and the ground environment of thrust augmented lift systems. The Russians have made tradeoffs to acquire a supersonic configuration with a significant vertical payload. The downside of the tradeoff is a logistical penalty for multiple, dissimilar engines and a harsh ground environment that carries its own logistical requirement. In summary, the experience afforded by this Russian VSTOL Technology assessment will guide us as we develop the next generation of powered lift, jet aircraft. 482 SECTION 4 Length - 50.8 ft Wing span - 24 ft Height - 14.3 ft Wing Area - 199 sq Maxntium TaJeeon Weight - 25,795 lbs SECTION 4 Legend 1 . Airspeed Indicator 2. Radar Altimeter 3. Mach Meter (?) 4. Altimeter 5. Main Attitude Gyro 6. Horizontal Situation Display 7. Vertical Speed Indiactor 8. Clock/ Stopwatch 9. Engine Tachometer 10. Fuel Gage 1 1. Nozzle Indicator 12. E.xhaust Gas Temperature 13. Lift Engine RPM (?) 14. Lift Engine Temperature 15. Hydraulic System Pressure 16. VSTOL Advisory Lights 17. Sideslip Indicator 1 8. Combined G Meter / AOA Indicator 19. Nozzle Control Button On Stick Fig. 3. YAK-38 Intstrument Panel 484 SECTlOn 4 Fig. 4. YAK-38 Left Console SECTION 4 Length ' 60 ft Wing span • 33.14 ft Keight • 16.4 ft Wing Area • 32219 sq ft nonal Weight Empty - 25794 lbs aum VTO Weigh: - 34760 lbs Maximum STO Weight - 42900 lbs Figure 7. THRUST VECTORING NOZZLE OF THE yAK-141 457 POWERPLANT CONFIGURATION SECTJON 4 OJD 'u o u Figure 8 488 loads YAK-141 LONGITUDINAL SECTJOn 4 Figure 9 489 490 SECTION 4

 

 

[SUBS17]

This is interesting.

 

And F35B's TVN is a different arrangement but with 4 directions.

 

Edited February 21, 2022 by SUBS17