N15TZ

On September 7, 2022, about 1453 mountain standard time, a Cessna 750, N15TZ, was substantially damaged when it was involved in an accident near Phoenix, Arizona. The pilot and co-pilot were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 positioning flight.

The pilot reported that shortly after departing Tucson International Airport (TUS), Tucson, Arizona, the landing gear would not retract. The pilot contacted air traffic control and requested to divert from the original destination and continue to Phoenix-Mesa Gateway Airport (IWA), Phoenix, Arizona. Soon after, he noticed that the hydraulic system “A” lost fluid and pressure. The pilot stated they completed the “Landing with No ‘A’ System Pressure” checklist. He reported that the landing on runway 30L was smooth and on speed at Vref, and that he immediately began using the emergency brake. The pilot reported that once the airplane was several hundred feet down the runway, the left main landing gear tires blew out, and that he used the rudder for directional control. At about 6,900 ft down the 10,401 ft runway, the airplane veered left off the runway; the right main landing gear subsequently collapsed.

Before the accident flight, when the airplane was parked in TUS, a mechanic reported that he witnessed the accident airplane leaking hydraulic fluid from the nose landing gear area, creating a puddle on the ramp. He reported the leak to one of the pilots, who said they were on their way to Iowa and would fix it there.

A video of the landing at IWA revealed that shortly after landing, two bright flashes of light were visible on the left side of the airplane. The airplane continued down the runway and suddenly veered left.

According to automated dependent surveillance - broadcast (ADS-B) data, the airplane was on approach with a groundspeed of about 154 knots as it crossed the approach end of runway 30L. (See Figure 1.)

Runway 30L is 10,401 ft long, with a downhill gradient of 0.4%.

Figure 1-ADS-B Flight Track Data.

The CVR recording captured one of the pilots, who was outside the airplane on the parking ramp, saying “it’s not water.” After boarding the airplane and preparing for takeoff, one of the pilots asked about the leak outside. The other pilot confirmed there was a leak but couldn’t identify the source. They also spoke about the right wheel and mentioned that “we’ll probably need to do something about that,” and discussed possibly having a hydraulic leak in the A system. After a flight planning conversation, they discussed the nature of the leak and that the ground crew mentioned it to the pilot outside and confirmed he could see something dripping but couldn’t find its origin. The pilots continued through their preflight checks and mentioned that everything was working properly. They mentioned the hydraulic systems and that they would “leave it up and see if it changes,” and that “as long as we got pressure everything should be fine,” and they would check the fluid once on the ground to see if it was hydraulic fluid.

During the departure from TUS, the landing gear would not retract after multiple attempts. The flight was diverted to IWA and again they attempted to retract the landing gear multiple times. They mentioned to air traffic control (ATC) that the gear was down and that they lost hydraulic System A. A checklist was performed and the power transfer unit (PTU) was “pulled.” They also discussed not having the use of normal braking during the forthcoming landing. They discussed the System A failure and “what hose blew,” and they both confirmed that System A had no fluid. During the communication with Phoenix approach control, the pilot confirmed that there was no emergency. After the landing gear was confirmed in the down position, the pilot reported that they had all the flaps possible extended, and that they were limited to 15°. A few minutes later the crew discussed the flaps again and referred to the flight manual. The flaps were then set to the full down position and, about 15 second before touchdown, the airspeed was called out at “160 knots.” Soon after the airplane landed, ATC notified them that the left main tire was “exploding,” and the pilot replied that they were having a brake problem.

The airplane came to rest in the runway safety area near taxiway H, with a directional heading of about 140°. The right wing was resting on the ground and the right main landing gear remained partially attached. The slats and flaps were fully deployed, and the right wing slats were buckled in several areas. The right thrust reverser was deployed, and the fuselage was buckled near the engine pylons.

A mechanic who arrived at the accident site to move the wreckage confirmed that hydraulic systems “A” and “B” contained no fluid. While the landing gear handle was in the down position, the “A” hydraulic system was serviced, and when pressurization was stabilized, no leaks were noted. The PTU line near the right landing gear attachment was damaged and hydraulic system “B” would not hold fluid or pressure when serviced.

A postaccident examination of the airplane revealed that the nose landing gear centering hydraulic flexible line was frayed and cracked near the upper fitting. The line was removed, and a cap was fastened to the upper fitting. The line was attached to a hydraulic servicing cart and was pressurized with hydraulic fluid. Hydraulic fluid flowed freely from the frayed area. About 1/3 of the left main wheel, tire, and brakes were worn down on one side. The hydraulic system “B” pressure line was damaged, consistent with impact damage from the right main landing gear collapsing The emergency brake handle was pulled twice at the pilot’s seat position and brake pressurization was heard from the left main landing gear. The left main wheel rotated freely on its axle.

According to the airplane’s operating manual, the hydraulic system is a dual closed center system. Pumps driven by each engine supply pressure for operation of the landing gear, nose wheel steering, anti-skid brakes, spoilers, speed brakes, roll control spoilers, elevators, ailerons, lower rudder, and the thrust reversers. The two separate hydraulic systems are identified as the A system and the B system. Redundancy is provided by the fact that the B system can operate the A system through a hydraulic motor/pump unit in which no fluid exchange takes place. An electrically operated auxiliary pump in the A system also provides backup power for equipment powered by that system. Pneumatic backup is also available for landing gear extension and braking. System A may be powered redundantly by two methods. In the event of a left engine or hydraulic pump failure, pressure can be restored to System A through the PTU. The PTU is a hydraulic pump driven by System B pressure. With System B operating at 3,000 psi, the PTU can generate 2,600 ±400 psi to System A. The second backup system is an electrically driven auxiliary pump that can provide 3,000 psi hydraulic pressure to all of System A. Due to low system capacity when the auxiliary pump is the only source of hydraulic power, the landing gear should not be lowered hydraulically or the thrust reversers deployed, since it would result in slow operation of other more critical systems.

According to the airplane’s flight manual the maximum certified landing weight is 31,800 lbs.

The Vref landing speed during the abnormal procedure, is defined as 1.3 times the stall speed with selected landing flaps of 15°. According to the airplane’s flight manual and the airplane’s reported weight at the time of the landing, the landing speed for the airplane would have been between 137 and 138 knots.

The following procedure is from the pilot’s abbreviated checklist for Hydraulic Volume A-B Amber CAS message.

HYD VOLUME LOW A-B (HYDRAULIC VOLUME LOW A-B)

Indicates a probable leak with low fluid quantity (<16%) and normal or low pressure

1. Hydraulic Pressure and Fluid Quantity - - - - - - - - - - - - - - - - - - - - - - - - - - -CHECK

2. HYDRAULIC PUMP “A” or HYDRAULIC PUMP “B”

Switch (as applicable) - - - - - - - - - - - - - - - - - - - - - - - - - - - - - UNLOAD

• IF “A” SYSTEM

3. HYDR B/PTU CONT circuit breaker - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - PULL

4. Land as soon a practical. Refer to Emergency/Abnormal Procedures,

LANDING WITH NO “A” HYDRAULIC SYSTEM PRESSURE; Tab P2

WARNING

DO NOT USE SPED BRAKES IN FLIGHT UNLESS “A” HYDRAULIC SYSTEM PRESSURE IS ZERO. OUTBOARD SPEED BRAKE PANELS MAY NOT RETRACT.

PROCEDURE COMPLETED

The following procedures are from pilot’s abbreviated checklist for Landing Gear Will Not Retract and Landing With No “A” System Pressure, Red CAS message.

LANDING GEAR WILL NOT RETRACT (NORMAL “A” SYSTEM HYDRAULIC PRESSURE)

Indicated by failure of red UPLOCK light to extinguish after attempting retract.

1. Landing Gear Handle - - - - - - - - - - - - - DOWN (airspeed below 210 KIAS)

2. Landing Gear - - - - - - - - - - CHECK DOWN AND LOCKED (3 green lights)

3. Land as soon as practical, do not retract landing gear.

PROCEDURE COMPLETED

LANDING WITH NO “A” SYSTEM PRESSURE

WARNING

• DO NOT EXTEND FLAPS BEYOND 15° WITH EITHER HYDRAULIC

SYSTEM DEPRESSURIZED. IF A SPEED BRAKE OR SPOILER CHECK

VALVE FAILS TO SEAT, UNCOMMANDED ROLL MAY RESULT. RETRACT

FLAPS TO 15° IF EXTENDED.

• DO NOT USE SPEED BRAKES IN FLIGHT UNLESS “A” HYDRAULIC

SYSTEM PRESSURE IS ZERO. OUTBOARD SPEED BRAKE PANELS

MAY NOT RETRACT.

BEFORE LANDING

1. Landing Data - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - CONFIRM

a. Airspeed - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - VREF (Flaps 15°)

b. Multiply normal FLAPS 15° landing distance by 1.6.

CAUTION

AVOID LANDING WITH TAILWIND OR DOWNHILL RUNWAY GRADIENT.

2. Crew Briefing - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - C...