EARLY YEARS IN THE HORNET’S NEST F-18 GROWING PAINS JACK ABERCROMBIE — DECEMBER 2016 SCOPE & PURPOSE OF PRESENTATION PROGRAM BACKGROUND TO SET STAGE FOR REST OF PITCH. MAJOR DESIGN CHALLENGES (EXCLUSIVE OF FIRE CONTROL, COCKPIT DISPLAYS, AVIONICS, the “ILLITIES,” the F -18L VERSION, or LEGAL ISSUES). ONLY LIMITED INFO ON PERFORMANCE, PROPULSION, AND STORE SEPARATION. MOSTLY ON FLYING QUALITIES / SAFETY OF FLIGHT ISSUES. USAF LIGHT WEIGHT FIGHTER (LWF) aka AIR COMBAT FIGHTER (ACF) COMPETITION “SHOW & TELL” DEMONSTRATORS GENERAL DYNAMICS YF-16 1 st FLY 20 JAN 1974 (UNPLANNED 6 MINUTE FLIGHT) NORTHROP YF-17 1 st FLY 9 JUN 1974 CONGRESS AUG 1974 DEMAND: NAVY ADAPT ONE OF THE AIRPLANES. (WINNER OF USAF “SHOW & TELL”— GD — JAN 1975). NORTHROP / McDONNELL TEAM MCAIR LARGE ADVANCED DESIGN VFAX ORGANIZATION CHANGED TO NACF — OCT 1974 (BEFORE END OF ACF COMPETION). McDONNELL / NORTHROP WON NAVY COMPETITION (COMPETING AGAINST GD / LTV TEAM) FOR NACF WITH McDONNELL AS PRIME — MAY 1975. NORTHROP NOTE — CONFIG DESIGN SHOWN IS FOR AFTER OCT 1979. F-18 CONFIGURATION--1976 • SCALED UP YF-17 LEX • THREE LEX SLOTS • SNAG WING LEADING EDGE • AILERONS OUTB’D EDGES WELL INB’D OF TIP • NO-SNAG STABILATOR • NOSE STRAKES ON SIDES OF RADOME NOTE: DESIGNATION “F - 18” AND “A - 18” OFFICIALLY CHANGED TO “F/A - 18” ON 1 APR 1984. F/A-18A AND B FOR ONE- AND TWO-PLACE TF-18 VERSIONS, (Cs AND Ds LATER). “HORNET” NAME ADOPTED 1 MAR 1977 ( AVIATION WEEK ADVERTISEMENT--19 APRIL 1976) MAJOR DESIGN CHANGES FROM YF-17 F-18 1 ST FLIGHT CONFIGURATION — NOV 1978 F-18 F-18 (GEAR FARTHER AFT) YF-17 S=350 ft 2 b=35 ft T=14,400 # x2 * TOGW=23,000 # * F-18 (1 ST FLIGHT) S=400 ft 2 b=37.5 ft T=16,000 # x2 * TOGW=34,700 # * (+4280 fuel) NOTE ADDITION OF: WING FOLD (2 ITERATIONS) SNAG WING LE (3 ITERATIONS) SNAG STABILATOR LE DUAL NOSE GEAR WITH TOW LARGER RADOME SLOTTED TE FLAPS / AILERONS LONGER LEX * MAY BE APPLES TO ORANGES MAJOR ENGINEERING PROBLEMS ANALYSES & SOLUTIONS --HIGH LIFT SYSTEM. --ELECTRONIC FLIGHT CONTROLS. --NOSEWHEEL LIFTOFF SPEED. --SUBSONIC DRAG. --ROLL PERFORMANCE. --ACCIDENTS --LIMIT CYCLE OSCILLATIONS. --VERTICAL TAIL FATIGUE. --TWO-PLACE CANOPY EFFECTS. --LOADS. NOT PRESENTED IN CHRONOLOGICAL ORDER NOR RELATIVE IMPORTANCE. EVENT TIME PERIODS OVERLAP CONSIDERABLY. HIGH LIFT CHALLENGES THIN WING. WING FOLD. SLOTTED FLAP/AILERON. SNAG. LONG LEX. LSWT TESTS — 417 HOURS BEFORE 1 ST FLIGHT. TESTS AFTER 1 ST FLIGHT LOW SPEED WIND TUNNEL — 782 HR. FLIGHT TESTS — 28 FLIGHTS: - OCT ’80—SEP ’82 - CHALLENGES MET ! ELECTRONIC FLIGHT CONTROLS (1) FIRST ALL-DIGITAL, FLY-BY-WIRE CONTROL SYSTEM FOR A PRODUCTION AIRPLANE. (F-16 — ANALOG INITIALLY, F-4 PACT — ANALOG) QUADRUPLY REDUNDANT CHANNELS. CONTROL STICK-GRIP FORCE TRANSDUCERS. BACKUP SYSTEMS--DIRECT ELECTRICAL LINKS (DEL)-ONE DIGITAL, THE OTHER ANALOG. DIGITAL DEL FOR PITCH, ROLL, YAW. ANALOG DEL FOR ONLY ROLL, YAW. REVERSION MODE TO MECHANICAL CONTROL OF STABILATOR FOR PITCH AND ROLL CONTROL. ELECTRONIC FLIGHT CONTROLS (2) NAVY EVALUATION OF FLIGHT CONTROLS DESIGN “FLYING QUALITIES DEFICIENT. POOR MANAGEMENT ATTITUDE. COUNTERPRODUCTIVE COMPLEXITY. SIMULATION WITHOUT ANALYSIS. NEED MORE AERO INVOLVEMENT .” AND THIS WAS FOR JUST THE CARRIER LANDING OPERATIONS!! ELECTRONIC FLIGHT CONTROLS (3) PROBLEMS WITH INITIAL DESIGN PHILOSOPHY INEXPERIENCE WITH DIGITAL CONTROL (THROUGHOUT INDUSTRY). ONLY LIMITED USE OF AIR DATA & AOA. MASKING OF AERODYNAMIC NON-LINEARITIES. TOO MANY FILTERS & INTEGRATORS — STICK FORCE INPUT, STRUCTURAL MODES, COMMANDING MORE ROLL RATE THAN AVAILABLE. STICK TORQUE — HARD-OVER STICK BUT NO ROLL RATE COMMAND. --TOO MUCH TIME SPENT CALCULATING .-- RESULT — EXCESSIVE TIME DELAY (150-200 MILLISECONDS) — PILOT- INDUCED OSCILLATION — (PIO) SOLUTION — SPECIAL DESIGN TEAM FORMED APR ’79 FOR “MAJOR SURGERY” NOSEWHEEL LIFTOFF SPEED AIRSPEED TOO HIGH (~150 kt)-OVER-ROTATION AFTER TAKEOFF. PROBLEM FLAGGED MONTHS BEFORE 1 st FLIGHT. SPANWISE BLOWING BLC UNDER TAIL VERY EFFECTIVE ~30 kt. BETTER SOLUTION — UN-SNAG STABILATOR, SCHEDULE RUDDER TOE-IN / FLARE AND LE FLAP DEFLECTION WITH AOA ~35 kt IMPROVEMENT. (MCAIR APPROVED JULY 1979). STALL LARGE WEIGHT MOMENT NOSE UP MOMENT DUE TO RUDDER TOE-IN NOSE DOWN DUE TO RUDDER FLARE NEW CHALLENGE — SELL INNOVATIVE SOLUTION TO NAVAIR CUSTOMER. SUBSONIC DRAG EARLY FLIGHT TEST RESULTS--HIGH CRUISE DRAG. SOLUTION —OCT ’79 - JAN ‘80— PLUG TWO FORWARD LEX SLOTS. STREAMLINE HEAT EXCHANGER EXIT COVER. INCREASE WING LEADING EDGE RADIUS TO ~1/4 INCH. LEX SLOT CLOSURE — SIGNIFICANT REDUCTION IN DRAG. INCREASED LE RADIUS —”BODACIOUS” IMPROVEMENT. (LEX SLOT CLOSURE — STAY TUNED FOR BAD EFFECTS). DANGEROUSLY LOW ROLL RESPONSE LOW ALTITUDE, HIGH SPEED (1) PLACARD — LATE 1979: NO ROLLS >360 0 at < 10K, > 0.8 MACH. INCREASED SPAN AILERON, DIFFERENTIAL TE FLAP — NO HELP. MCAIR PILOT NOTES WING FLEX DURING ROLL. MODEST WING STIFFNESS INCREASE (ADDED PLIES) — NO HELP. DISCUSSIONS —JAN ‘80— DIFFERENTIAL LE FLAP — TWIST WING FOR ROLL. TOP NAVY/MCAIR MGT DISCUSSIONS-WING PROBLEMS —18 MAR ’80. UPPER LEVEL MCAIR ATTENTION —4 APR ‘80 -- 6 MAY ’81 --26 MEETINGS ENGINEERING MANAGEMENT, MANY IDEAS. MANAGEMENT REVIEW MOVIES OF WING TWIST DURING ROLLS-- 21 MAY ’80 DANGEROUSLY LOW ROLL RESPONSE LOW ALTITUDE, HIGH SPEED (2) SOLUTION DIFFERENTIAL LEADING EDGE FLAPS / WING TWIST FOR ROLL CONTROL —FLIGHT TEST APR ’81 -- v4.3.2 PROMs & NOV ’81 --v6.0 PROMs. WING WARPING CAN BE BENEFICIAL ! ACCIDENTS and NEAR ACCIDENTS APR 1980 — JUN 1987 MAIN GEAR AXLE BROKE — STILL LOOKING FOR WHEEL NEXT DAY. TF-18 LOSS — AFTER FARNBOROUGH — ENGINE TURBINE DISK FAILURE. MCAIR PAID FOR LOSS--$38M. LOSS —SLOW RECOVERING “FALLING LEAF.” (MORE INFO FOLLOWS) SPARROW MISSILE HANG FIRE-14 SEC BURN. SCARY. AIR-TO-AIR BOMBING VICTORY — A4 CHASE (LOSS) MK-82/VER DROP. LOSS — LH LE FLAP FAIL FULL UP. LOSS AT EL TORO. LOSS NEAR SAN CLEMENTE. LOSS WITH PILOT AT MIRAMAR — MAIN GEAR PLANING LINK FAIL. BLUE ANGELS LOSS —FLEW INTO WATER TESTING “SCREEN DOOR SPRING” FEEL SYSTEM. BLUE ANGELS LOSS — INVERTED, DUAL FLAMEOUT AT EL CENTRO. LOSS — ENGINE COMPRESSOR BLADES FAILURE. FALLING LEAF 14 NOV 1980 — Lt TRAVIS BRANNON, F-18 #12 WITH LEX SLOT CLOSURE MOD — ACM @ 23K — “FALLING LEAF” SERIES OF DEPARTURES. RECOVERY CONTROLS AT 14K NOT EFFECTIVE. EJECTED ~6 or 7K. NOT A SPIN (SPINS THOROUGHLY INVESTIGATED BY MCAIR TEST PILOT). PARTIAL SOLUTION v10.7 PROMs, 2003 WITH BETA & BETA RATE FEEDBACK USING INS INFO, etc. PILOT HANDBOOK: RELEASE CONTROLS AND WAIT! LIMIT CYCLE OSCILLATION — 5.6 Hz LATERAL ACCEL AT PILOT — 1 g PEAK-TO-PEAK 1st OCCURRENCE 4 JUN ’81—OUTB’D BOMB and AIM -9 MISSILE--0.97M, 10K. MANY “SOLUTIONS” IN NEXT 5 YEARS— ALL TURNED OUT TO BE ONLY “IMPROVEMENTS.” USN- JAN ’82—DECLARED 5.6 Hz OSCILLATION “SAFETY OF FLIGHT” ISSUE. MCAIR PILOT -- FEB ’82 -- ALMOST EMERGENCY JETTISON OUTB’D BOMBS. USN-- SEP ’82 -- ”OPERATIONALY UNSUITABLE.” ANOTHER “FINAL” FLIGHT CONTROL SOFTWARE CHANGE ~1986— ACTIVE OSCILLATION CONTROL (AOC) OF AILERONS APPARENTLY REDUCED PROBLEM TO “NUISANCE” CATEGORY INSTEAD OF “SAFETY OF FLIGHT.” VICTORY DECLARED AGAIN ! VERTICAL TAIL FATIGUE LEX VORTICES, SPEEDBRAKE--HOSTILE ENVIRONMENT. 1981 — CRACKED LUG IN ALL AIRCRAFT — DOUBLER ADDED. 1984 — MORE CRACKS IN ALL AIRCRAFT — NAVY GROUNDS FLEET-- “TIGER TEAM” FORMED. “ANGLE IRONS” ADDED. PROBLEM CONTINUED. 1985 — WIND TUNNEL TESTS: LEX SLOTS OPEN AND/OR LEX FENCE — GREAT IMPROVEMENT ! (AERO & STRUCT DYN IRAD) 1987 — 1 ST FLIGHT TEST LEX FENCE — RESULTS VERY GOOD. 1988 — NAVY APPROVED LEX FENCE FOR PRODUCTION. “ANGLE IRONS” LEX FENCE TWO-PLACE CANOPY DESTABILIZES DIRECTIONAL STABILITY AERODYNAMICS AT ALL CONDITIONS SAGA OF TF-18 #24 JAN ’84— “ROLL - OFF” AT 20 DEG AOA. MANY IDEAS TESTED--NONE HELPED: CHANGES TO BLD, SWAPPED WINGS, SWAPPED RADOMES. JAN ’85– RUDDER TOE-IN FLIGHT TEST — SIGNIFICANT IMPROVEMENT. PLANS MADE FOR PROM CHANGE AND NAVY TEST. APR- MAY ’85— NAVY DECLINED TEST. ACCEPTED TF#24 w/$1 M PENALTY APR ’87— AGGRAVATED CONTROL TEST WITH CENTERLINE TANK (WHICH HURTS LATERAL STABILITY). TANK BROKE OFF, DAMAGED A/C. SOLUTION (?) — PILOT HANDBOOK AOA PLACARD--TWO-PLACE AIRCRAFT — 20 DEG--M=0.7, 12 DEG--M>0.9. (NO LIMIT BASIC SINGLE PLACE) NEGATIVE DIRECTIONAL STAB AOA > 20 DEG. MUCH WORSE THAN SINGLE PLACE AIRPLANE.