Testing the Flight Controls | F-4 Phantom
Vložit
- čas přidán 6. 07. 2024
- Today we made good progress on the Phantom! Tested out both the PC-1 and PC-2 hydraulic systems, and we get the see the electrical system come to life!
For those of you that are on Instagram, check out Jack's page, as he regularly posts stuff from the hangar. His page is at:
/ jones.aviation
Our maintenance work and flight operations are funded entirely by donations. If you'd like to help keep these iconic aircraft operational, please consider donating!
Main website:
www.collingsfoundation.org/
Donate Online:
www.collingsfoundation.org/gi...
Sponsor the F-4D or other specific aircraft in the collection:
www.collingsfoundation.org/gi...
Become a member of the Collings Foundation and American Heritage Museum:
www.americanheritagemuseum.or... - Auta a dopravní prostředky
My Uncle Jim Dutton was a USAF flight instructor teaching pilots how to fly Phantoms. He passed away this year and it's really cool being able to see y'all bring the bird back.
From Yellowstone? The Dutton ranch!!! That’s cool, say hi to teeter for me
@@joseywilds3133what part didn't you understand he passed away 😮
Airman are E-1s in the Air Force just fyi
@@enricomandragona163dutton....Dutton ranch...Yellowstone...the TV Show
I never realized it was the only flyable F-4 in the states! Terrific work
@@sam_mccrmck I just learned of this myself😳. That’s a tragedy there is only one flyable phantom in the US! One of the most iconic birds of the century doesn’t have any buddies to fly with?!?! WTH?!? Lol
Really what a shock! We recall Seattle's Blue Angel Air show, (Boeing fields Seafair) 14 years ago. They featured an F4 Phantom, It was a formidable demonstration! Now just one?! 💪🏼🇺🇸 🌍
@@jasonwhite5125key word is flyable.....only 1 that's flyable (right now) many people are (many as in a dozen or so) are attempting to get their F-4s flyable
@@sam_mccrmck I hope the others do get theirs flyable! Then they can grace our skies with more LEGENDS😆😆🤷♂️
As Crew chief on USAF F4C, D, and E aircraft in the 70s, I remember doing all these things. I actually got to fly in an F-4 (a D model) in the back seat and the pilot allowed me some stick time. It was an awesome experience! Yours looks like a D model. I see that is has leading edge flaps instead of slats and it has the formation lights installed. I also notice that stabilator does not have slats. I could not see if the rear view mirrors are installed on the canopies. I noticed a few changes that were not on the aircraft I worked on, for example the digital display where the combining glass used to be and the HSI and ADI were replaced with a digital display.
Killing it. So great to see the F-4 come to life and respond. I’m a firm believer in mechanical things have a soul. They want to run and do what they were designed for. I’ve taken cars that have been sitting for 30 yrs locked up engines no brakes nothing and get them running and moving again. Military stuff especially gets beat and put up. But that’s how they like it. So the Phantom will fly for sure they just need our help staying in the air.
Cars and aircraft nothing alike, the standards to get an aircraft up to standard to fly are 100 times harder.
Great to see Spook is coming to life.
When performing engine runs, the area infront of the intakes (about 4 meters minimum) has to be well cleared of FOD, including loose concrete, pebbles)
If you're going to run up to anything close to high power, there should be nothing thet could work loose located behind the jet.
Well done on the electrics. Go make some NOISE !
Believe next week we only doing low power checks. It’s mostly to start up the engines, and also allow all the hydraulic pumps to run and help bleed any trapped air. We’ll top off the engine oil afterward too. We may even do a low speed taxi check, but not sure on that. Looking forward to making some noise too!
I used to work for thunder aviation when it use in business in the 80’s. We had OV-1 mohawk, two t-33’s and 2 F-8 Crusaders all in running condition
I was a weapons loader on F-4 C's and D's in the late '80s based at McConnell in Wichita, KS. They had more
sharp edges than a nuns' ruler-when working underneath we wore Navy hard cranial helmets to avoid head
shots. You weren't considered a member of the fraternity until you received your first "Phantom bite." Most
of ours were veterans of Vietnam.
Same here. I still have scars on my back from ducking down while driving the jammer loading SUU 23 gun pods on the centerline.
@@heeder777 Ah yes, the SUU 23 gun pod-I was the only one that had a skinny enough hand to connect the cable to the aircraft. One night we had 3 crews loading 8 pods, one to hang, second for the functional check, and
one to safety wire.
Awesome!! If there’s an engine start next weekend: bring every damn camera possible! We need ALL the footage from every angle 😂
Awesome channel, can’t get enough, especially the F-4! Watching all this brings back a flood of memories! The -60, hydraulic mule, start cart…all that AGE goodness! Worked avionics on F-4 C’s and D’s with the Michigan Air Guard, 191st FIG, Michigan Six Pack, one of the most recognizable tail flashes in the Air Force!
So it’s true. You do have a Phantom. You sneaky Texan. Yes I was the one that ask about a flyable Phantom in the F-100 video. Please let me know when you guys fly this beautiful bird. I will be driving from The heart of Dixie. Thanks for posting this.
Really Great Progress on the Phantom yesterday we ran the CF TA-4 we fixed one of the Hydraulic Problem we still have one more to go great progress on the TA-4.
That hydraulic power cart is awesome, thanks for showing that
My pleasure! Wish it didn’t leak so much, but it does the job.
From my USAF Crew Chief days we woul have 3 people on headsets. The operator at the cockpit controls, the mule operator and the supervisor watching everything. It is good for safety.. Oher that that, GREAT JOB! The last F-4 that I'd seen fly was the one that went on static display at Eielson when they flew it in.
Another one hitting the sky’s fantastic.
Indeed!
Saw an F4 do two passes at Sun N Fun about 20yrs ago. Very impressive. Which I could have seen them fly more.
For once, I can say thank you to the CZcams algorithm.
As a former Viper, Night Hawk and Raptor Crew Chief it's wonderful to see the testing go so well. Seeing that style mule brought back a lot of memories for me. I always enjoyed using them once you learned the tricks to operating them correctly. Especially the newest ones made for the Raptor and it's 5000 psi hydraulic systems which were VERY particular with getting the system bled. Even more crazy, you actually ran that mule in "test stand" while connected to the aircraft for some tests.
If all goes well, I know how Phantoms can be a PITA, I hope she'll make it to Wings over Houston. Seeing her fly in person is worth the trip down there from my area of Texas.
She'll always be at Wings Over Houston, hopefully as a flyer this year but we'll see on that! 5,000 PSI, yikes!
@@DieselThunderAviation Yikes indeed! I had a 3000 psi pinhole leak cut a rag in half while chasing down a leaking line in the F-16 vertical stabilizer that went to the rudder ISA. I am so glad it wasn't my fingers I was using to check for leaks while flexing the line. So I was always very aware of the Raptor's hydraulic systems pressure and what it was capable of. However, boy did that increased pressure make those flight control surfaces move like lighting on the Raptor.
I was an AME in R.V.A.H.-3 in the Navy, RA5C, TA3B, TA4J. I was shocked to ear you say that this F-4 was the only flyable in the U.S.!
Would love to see a Flyable RA5C!
wow! I just remember airshows in the late 80s early 90s how LOUD this plane is. I loved seeing the F14s fly for the swept wings but this beast was so loud it got everyone's attention!
She is still quite loud, even at idle! Really looking forward to seeing her in the air someday!
Amazing! Really looking forward to next week’s episode and hopefully all will be ok. Well done Team !
AO3, I was Plane Captain for 2 years in the early 70's on the F4J while stationed at NAS Miramar CA. I was so proud of knowing that plane inside and out. Twin J79's. Just an awesome aircraft.
Thank you for your service! J79's sure sound good! I imagine there's quite a bit of difference between the backseat of a Navy Phantom vs. an Air Force Phantom?
This brings back so many memories! I was Airframes on Prowlers back in the day and this was a nice walk down memory lane. We used an NC-10 and Jenny for our stuff but still super dope to see a similar thing on the F-4. Thanks for posting this!
Having the Huey fly with the bombers during the WoF Texas stops was awesome. I miss those days.
Love the Huey, would definitely like to see her fly again!
Glad I found this channel. Grew up around Goldsboro, NC. Spent a lot of time watching F4s from Seymore. One of the motivators to join the AF back 88 :) Parachute Survial Equipment at Nellis, got to pack quiet of few f4 drag chutes for transient aircraft but never packed the Martin Baker ejection seat chute, well once in tech school. We mostly packed the ACESII. Glad you all are keeping one Alive! Thanks for sharing.
I haven’t seen an NC8 power cart in a long time. Worked on F/A-18 A through F’s. In the early 2000’s we had a few NC-8’s floating around..
I'm so happy to see this bird come back to life. I need to get up there for the airshow later this year.
CZcams just recommended this. Superb ! Will go watch your other videos. Thank you for the hydraulic mule explanation, big fan of technical stuff / geekery. Amazed this is the only flying Phantom in the US. all the best folks
so nice to see you all are bringing this plane back to life. Luckily I was able to witness one of the few remaining ones flying many years ago in the mid 2000's at an air show at Joint Base MDL in New Jersey. The sound from those engines will rattle your soul. Good luck with it and look forward to the flight video. Thanks!!
always power up the hydraulik system after a long pause,with reduced hydr.power so start with approx 500 psi,then move all aactuators,be aware with the flaps,they have a internall mechanical up lock ,wenn air is in the actuator and the lock opens you can damage the flaps with a loud bang. .tip from a "hangar bongo"
Crossing my fingers that all goes well and we hear those engines next weekend
Seems like things are moving faster and faster lately. Awesome work, keep up the pace and she'll be flying in no time.
Now and then we would get a few of the 507th's come in for fuel. Loved watching them do touch and gos as tinker would run them off. Miss hearing the bleed air on final
I can’t believe it’s the last flyable example- heck I remember flights of these and Guard versions in the tarmac. Glad to see you keeping them flying
Last flyable one in the U.S. at least. Three countries still operate these; Greece, Turkey, and Iran. We're working to put this one back in the air!
I wonder if this is the same f4 I saw fly in Michigan in 2010. A real beauty she was
Sweet...lots of hard work to get to this point......
Good job all !!!!!!!!
Would be cool to have the hun and f-4 fly at WOH!!!
Another awesome video. Maybe you could make a video detailing that hydraulic cart and the electric power cart. How the work, their engines, start and run procedure and what hydraulic pressures and electrical voltages AC/DC that they supply.
Do you have plans to fix them up/ refurbish them to make them look nicer and function better (you said one leaked)?
The phantom is one of my favs! If you don’t know the story of Brigadier General Robin Olds, ( formerly Colonel in Vietnam when he flew phantoms) and you love the phantom, you have to look up his stories from WW2, Korea( I think😬) and Vietnam! He is a Phantom Legend!
Amazing video!! Very glad to see this channel getting the views it has long deserved!! I’ve tried to like and comment on every video so the YT algorithms will ‘catch on’ quicker. There is so much content in those hangars, you have yourself a gold mine (of content, and revenue hopefully). I just wish I would have known about the CF when I used to live in The Woodlands. Keep up the awesome work! -Josh in Concord, NC
Engine start!!! Let’s hear that beast roar and howl!!!
i worked on these in Saudi Arabia, in 1992. I also learned ABDR at Hill AFB in 1991 on the F-4.. 2A753 (USAF), 15G (Army Guard),, IYKYK
Be very careful. There have been 1,867 safety incidents involving the Phantom. When I was in the Air Force back in the 1980s, Flying Safety Magazine always had a notable incident on the back page. It was always an F-4.
WOW, so D*** exciting! Congrats...
Worked hydraulics on the B-2 Bomber; loved to see the hydraulic MULE out there working. Noticed you set it at 3000 psi-our working psi was typically 4250 on the bombers; looks cool!
Great to see the F100 fly, not its the F4's turn Shes such a beauty!
I know for a fact that maintaining WWII and Korean War era aircraft is expensive, i can only imagine the amount of $$$ and time it takes keeping Vietnam War Era birds airworthy!!! These aircraft are waaaaaay more sophisticated and labor intensive. I'd like to help. It won't be much, I'm not wealthy...and I'm trying to get the Amphibious Tractor Association Memorial built at The Museum of The Marine Corps...But please, I want to help any way I can. Thank you for keeping these beautiful girls in the air...Watching that ol F-100 hit her afterburner again!!!! Gave me chills!!! Semper Fidelis and as always YAT-YAS!!! PALADIN SENDS
Awesome!
Nice to see her moving her "feathers". Can't barely wait to to see her making some noise 😁.
Oh, she made some noise alright! Think you'll like the next video.
I certainly did, man 👍.
My favourite airplane. Sadly due to defence cuts in the UK I never had the chance but went the civvy route to flying. 20K hours later I still feel the need……..( you know the rest)
Ooh that is quite the beautiful sight, hopefully this means she can be up and running some point "soon" 😂
Here’s hoping the engines run out good and no quirks of vibrations from setting to long. Seen an engine that had an aft bearing starting to seize up and twisting the struts before it was shutdown in flight.
@@user-kp5st5jw9i Perhaps an oil change after the run ?
cool stuff
Gr on dcs is going to love this ! You guys should do a video tour together
I was a Avionics Specialist at Homestead 83 to 85
680 was one of my jets
Cool! Do you know which 680 you worked on? Ours is painted to look like the F-4C that Colonel Olds flew in Operation Bolo, which was 63-7680. That aircraft was shot down in November of 1967.
I hope you can get an F-104. I know there was a 2 seater at the USAF museum in Dayton. Has hurricane damage, but still worth aquiring, and maybe with enough funds and volunteer work can be air worthy again.
Unfortunately I don't think the USAFM sells or parts with their aircraft they should acquire planes of fames f104 complete with Vietnam era paint job
GENTS, YOU REALLY NEED TO GET YOUR HANDS ON THE A6E INTRUDER
Completely agree only replaced by the f-18 grew up in Tri-Cities Washington they flew all around Hanford nuclear facility when I was a little kid a6 intruder is more than deserving of a display team
CANNOT WAIT!!!! for the engine start...this is such an iconic a, it really is, and it's amazing it even flew, thank you for sharing this journey with us it is TRULY A PRIVELEGE. Do you have a patreon? I'm sure A LOT of people would donate.
Dig it!!!
That is just awesome! Would love to see this bird fly:)))
You and me both!
former F35 crew chief.As much as i love the F4, i dont think i can work on anything below 5th gen again. 😂
Amazing how Korea just retired their F-4 Phantoms just last month! Have them send over some airframes for spare parts, right?! Or have some recent maintainers from there come over and share some recent lessons learned, fresh in their minds. ... It would be easier than stealing a current Iranian F-4 (they have around 50), as the last Top Gun movie showed it's really kind of hard to get away with that, .... but fun! ..... I worked for McDonnell-Douglas near the factory that made the F-4, and I was late by 1 year from the end of production. Harriers, Hornets, and Eagles kept everybody super busy in the 1980's though.
🎉, gear swing!
From what I can remember the Utility system runs the gear, Aux air doors, and speed brakes? Correct? Also when pressure is on the Utility system and electric power is on ,whenever You loose electric power the speed brakes and Aux air doors cycle. Hard to believe I remember all that!
So cool! Your son sitting in the cockpit looks like a young version of Rooster (Bradshaw)
from the film Maverick. :)
It appeared that trim settings were also tested, yes? Very happy to see the progress. Keep em flying!
Nose trim works, yes. Very hard to see externally since it doesn’t directly move the stabs. We’re pretty happy with the progress as well.
@@DieselThunderAviation I saw the stab move in small increments positive and negative and return to neutral. Pretty cool.
Are you guys taking applications for aircraft mechanics?😂 seriously, this is my dream job
I'm confused. Why would you not run PC1 and PC2 at the same time? We always ran both systems at the same time. MCDILL and DANANG. 69-72
Limitation of our equipment in our case. We don’t have enough hoses, and kinda hard to justify buying a couple sets of them (they aren’t cheap) on something that is used sporadically.
As a former AGE mechanic I saw you operating the Mule, hydraulic test stand, and nightmares returned.
I bet they leaked just as much then too!
@@DieselThunderAviation Yes, I was a lovable smart ass back then so my CAT leader always put me on them. When the driver would pull in a broken one he would pull me off of whatever I was doing and set me on it. No matter how good I got at fixing them I still hate them to this day.
@@britishrocklovingyank3491I came to see if any other AGE Rangers were gonna comment on the “Hydraulic Power Cart” comment…😂
If a mule isn’t leaking, it’s because it’s empty!
Any time you connect those hoses to an acft, you introduce air. The mule is designed to remove the air from the aircraft’s hydraulics. Nice work!!
@@Ontheflywithben Hell yeah!
Kinda looks Africa Hot there!
Have you ever thought of purchasing one of those 360 cameras so you don’t have to really worry about angles?
Only recently learned of those, certainly going to look into it!
This is great news! I guess the right main gear must be all back together. Did you guys do a gear swing or do you plan to do one before flying?
Indeed it is! Gear swing is on the list to do and is required in order for us to re-rig the gear doors properly. We also want to make sure that the gears move like they are supposed to as well.
haw about the gear and brakes ?Keep at it u still have a long way to go
Sure do, but we're getting closer! We'll be doing gear swings again soon, just need to put her up on jacks again first.
Sounds like a little Detroit 2 stroke in the pushback/GPU thing
That is the NC8, and it's basically a self propelled aircraft generator. And yes, it has a 4-71 Detroit Diesel under the hood!
F4 great plane
❤❤❤
👍🏻
where is this
Is there any chance of seeing the 100 or the Phantom at Sun-N-Fun 2025?
You should get a F-104 Starfighter, there is not enough footage coming out of Kennedy space centre. 😂
Not many of them left flying, only 3 in the U.S. I believe. Has a J-79 though!
@@DieselThunderAviation i know, i follow one of those pilots on YT, i think its a shame they dont post a lot of videos. We need more F-104 videos 😈
When you had the hydraulic pump running, how come he didn’t swing the gear?
The gear is on the Utility hydraulic system, and that task also requires the aircraft to be up on jacks to do that.
Congrats on the flight controls/hydraulics test! Can't wait to see her up in the air again where she belongs. Can you say who the current owner is? Does it still belong to the Collings Foundation?
Thanks! And yes, the Foundation has ownership of this aircraft.
How do you replace burned put bulbs for the annunciator panel?
Each individual indicator can be opened by pressing on the left(?) side and it will rotate open. There are 2 very small bulbs which can be replaced.
Is that asbestos based paint on that hyd pump???
I hope not
holy shit.. you have people actually walking under moving controls?
At 10:45 you point the camera at the base of the seat rails in the rear cockpit and the written comment "They're both working!" flashes on the screen. What were the things still working?
The two transformer-rectifiers that are mounted there. They are essentially large 28 Volt DC power supplies that are fed from either the 115 Volt AC ground power, or the engine driven generators if those are running. Since these are both mounted behind the ejection seat (which is out of the aircraft currently), it's nice to verify that that they are indeed working!
So I take it from your intro this a/c is only a replica of an actual tail number that got a Mig kill?
Sort of. This Phantom is a D model and never saw combat, tail number 65-0751. The Foundation wanted her to be more representative of the Vietnam era, so on her last repaint she was painted as the F-4C that Colonel Olds flew for Operation Bolo. The aircraft that he flew that day was tail number 63-7680, and the only deviation on the paint job is the addition of the crew names on the nose.
@@DieselThunderAviationgotcha thats what I figured. I didn’t know the history of that particular tail number. Colonel Olds was my hero growing up. Went all the way into ROTC in the 80s only to kearn my eyesight wasnt good enough. So I enlisted and became a aircraft maintainer. Wasnt much work in the civilian market for an old egress troop. Thank you for keeping our historical aircraft flying. I hate to see these Phantoms and others F-16s etc as drones! I have seen one F-4 flying at airshows, but maybe its no longer flying. I idolized the Phantom as a kid. What an awesome aircraft.
I crewed F4d models back at nellis and I can’t remember do the wings fold hydraulically or manually I want to say either way works?
I worked on the E Kurnass. Our wing tips were folded or deployed manually, they are heavy. The locking mechanism is also operated manually from under the wing. Got to make sure that indicator is all the way down & flush with the upper skin.
I believe all Phantoms except the E models (and some G models that were converted from E’s) have the hydraulic powered wingtips. Air Force Phantoms have the controls in the left gear well to fold/unfold them. Navy and Marine Corp Phantoms have it controlled by the pilot if I am not mistaken for carrier operations. The locking mechanism is still manually operated at each wing, I’ll be sure and show that next time we move the wings. Not sure why the E had manual wings unless it was a weight saving thing.
@@DieselThunderAviation Our "Hammers" Kurnass E 100% had manually folded wing tips.
The wing tips were almost always down and locked, even in our B-Check shop.
I imagine that is pretty normal for a land based Phantom. I’ll have to ask Crew Chief Al what they did over here when they were in service, and how often the wings were ever folded.
@DieselThunderAviation it was weight saving. The Air force didn't need wings that could fold and unfold. So they removed the hydraulic system. Freed up weight for more ordinance or longer flight.
It's nice to see life in the ol' girl and her getting to stretch and move again. Why the difference in movement/height between the aileron panels? I presume you've already swung the gear after R&Ring the starboard main? As always, thanks for sharing.
We think the lateral trim was moved. Hard to correct without all of the systems running together. If we start her up next week, we’ll neutralize that trim.
@@DieselThunderAviation Cool deal, thanks for the info and I'm looking forward to the run up even if we won't be able to hear it for beans. SO! much better in person. 🙂
I didn’t see any ailerons in this video. The panels on the top of the wing are spoilers. The ailerons on the Phantom only move down and the spoiler on the opposite wing moves up.
Will you be able to purchase parts from the recently retired South Korean F4's?
Unfortunately not. It is extremely hard to get parts from foreign countries (even allies) due to ITAR restrictions. The State Department and Customs also factor into that too.
You should look into getting a B58,I know that they were a bitch to fly and keep in flying condition, just a thought 😊😊
Almost all B-58s were scrapped in 1977. Only one still has engines, 59-2458 at the NMUSAF at Wright-Patterson. There are only seven B-58s left that are mostly intact. There was also a derelict B-58 at Edwards AFB but it is so incomplete that last I heard, there were plans to scrap it.
Anyway, there are no B-58s that will ever fly again. My father was stationed at Carswell in the 1960s, and I still remember watching them fly. As much as I'd love to see one fly again, it's never going to happen.
Man, I haven't seen a Mule in years. Do you guys have an AGE mechanic? What? No -60?
Don’t think we have anyone that did AGE while in service. Couple of us are fairly good with them and we have a set of manuals for that stuff too. We do have a -60, that’s just over in another hangar. The NC8 is a bit more fuel efficient when we just need electrical power!
Does the F4 use skydrol?
No, she uses MIL SPEC 5606 hydraulic fluid.
Where is 680 from? FP doesn’t show up in the AF search for aircraft tails.
It’s a bit of a misnomer. This D model is painted to look like the F-4C that Colonel Olds flew for Operation Bolo. The tail number that he flew for that mission was 63-7680. The real tail number of our D model is 65-0751.
Actually, it's 65-0749, hence the N-number N749CF @@DieselThunderAviation
Wait was that a NC-8 power unit?
Sure is! Detroit Diesel under the hood and all!
Haven't seen one of those since the early 2000s when the Navy got rid of them for NC-10s
👀👀
Is the older fellow your A/R man?
Is this N749CF?
She sure is!
You guys prepped for Beryl?
Short answer, yes. The hangars have withstood up to Cat 3 and 4 storms. Sometimes the wind has damaged the rain gutters on them. We make sure everything is secure, and close the cockpits in case the roof leaks.
@@DieselThunderAviation good to hear! After making the announcement about doing engine runs next week, my first thought was how every would fair with Beryl. Good luck and can't wait to see an engine run video!
One sexy plane
A Continental gasoline engine???? That's weird!
Kinda thought the same when I saw that the first time also! Horizontally opposed 6 cylinder.
I forgot, what kind of F-4 is this?
if im correct they used this phantom to model the one in dcs, which is the E variant
I think it was the F-4D but i might be wrong
@@cornexus1051 I think the WSO cockpit is a bit different than the cockpit in the DCS version
@@alpenfoxvideo7255 It is either an F-4C or D, due to the lack of an internal gun :)
Our Phantom is a block 28 D model, and she didn’t get much in the way of upgrades. She still has the original DVST scope in the backseat (Direct Video Storage Tube). The variant in DCS is a block 45 E model. That one features more of the Phantoms upgrades, like the DSCG scope (Digital Scan Converter Group) and improved radar. Aside from the long nose and gun, there are a lot of similarities between them and a lot of the systems are identical. A lot of our manuals cover E models too and those have callouts if there are differences.
Crazy how much power is needed just to test the aircraft. Two fossil fuel generators, the aircraft systems must be incredibly inefficient.
Ground support equipment is still used with modern aircraft today too (civil and military). Older aircraft like this require this stuff as they didn’t have a self start capability. In the case here, one cart is supplying electrical power, the other with hydraulic pressure to operate the control surfaces. These carts are a lot more fuel efficient for testing, as you would otherwise have to start and run the main engines in order to have electrical and hydraulic power on the aircraft.