Secondary Power

[strikeeagle]

Here’s what we call the “secondary power” on the 15.  Just some geewiz so you can see what it looks like.

1 CGB, 1 JFS, 2 generators, 4 hydraulic pumps, 2 AMADS, and the panels that cover it all.  If we’re at this point in maintenance, it’s going to be a looong night or two on swing shift.

 

[Rainmaker]

Second time I tripped over that gargantuan drain pan, it would become a frisbee to the best of my abilities. 

[strikeeagle]

47 minutes ago, Rainmaker said:

Second time I tripped over that gargantuan drain pan, it would become a frisbee to the best of my abilities. 

I wonder what's wrong w/the jet.  Minus a motor and the CFT removed.  Along w/the entire sec power package.  It can't be good.

[Rainmaker]

42 minutes ago, strikeeagle said:

I wonder what's wrong w/the jet.  Minus a motor and the CFT removed.  Along w/the entire sec power package.  It can't be good.

Remove an AMAD…bushing falls out or mic checks bad…this is the result. A big metal jig that sets it all. 

[davidrbarnette]

2 hours ago, strikeeagle said:

Here’s what we call the “secondary power” on the 15.  Just some geewiz so you can see what it looks like.

1 CGB, 1 JFS, 2 generators, 4 hydraulic pumps, 2 AMADS, and the panels that cover it all.  If we’re at this point in maintenance, it’s going to be a looong night or two on swing shift.

 

Cool pic. How many people staff a maintenance operation to keep a squad of Strike Eagles flying? Is the F-15E "reliable"?

[strikeeagle]

1 hour ago, davidrbarnette said:

Cool pic. How many people staff a maintenance operation to keep a squad of Strike Eagles flying? Is the F-15E "reliable"?

About 300 or so maintainers each squadron.  It's the most used combat jet in the AF inventory.  Ops tempo has been through the roof since DS1.  Reliability is relative.

 

Edited July 31, 2023 by strikeeagle

[strikeeagle]

1 hour ago, Rainmaker said:

Remove an AMAD…bushing falls out or mic checks bad…this is the result. A big metal jig that sets it all. 

I figured that’s why it’s all laid out.

Edited July 31, 2023 by strikeeagle

[draconus]

18 hours ago, strikeeagle said:

 

 

So instead of all those parts you installed anti-gravity drive?

[AndyJWest]

5 hours ago, draconus said:

So instead of all those parts you installed anti-gravity drive?

They fill them with helium to improve accessibility during maintenance. The tailhook is being used as a mooring line. 

[t_hedlund]

That is a great picture, I enjoy seeing where the various components go, it makes easier to understand how they are all connected. 

[Rainmaker]

On 8/1/2023 at 11:57 AM, AndyJWest said:

They fill them with helium to improve accessibility during maintenance. The tailhook is being used as a mooring line. 

I wish they were. Generators are over 100 lbs.  Shouldering them is a back breaker. Got the MRIs to show for it. 

[ARM505]

I need an 'idiots guide to wtf a JFS is'.

I know APU's (use those every day at work), electric start, cartridge start etc, but have never taken the time to get JFS units. So.....what are they? What principle do they work on? Do they really start as fast as depicted in this module? Do they need warmup time? I assume they run on jet fuel? Are they just small APU's (ie. small gas turbines?) Anyway, it looks relatively small at least (I assume it's the thing in the middle of the other two things on the left in the photo - my guess is CGB (central gear box?) then JFS, between two gennies, then the hyd. pumps, and the AMADS on the outside?)

For my next lesson, I'll learn what priniciple of magic an F16 uses to start....or wtf an EPU is....

Edited August 3, 2023 by ARM505

[draconus]

37 minutes ago, ARM505 said:

I need an 'idiots guide to wtf a JFS is'.

From manual: "JFS is a self-contained small jet engine mounted on the central gearbox. JFS together with AMAD provide rotation and electrical power necessary to start the engines."

It has 2 accumulators. CGB is for selection which engine is spooled at the time. This is my layman knowledge.

https://pwoodford.net/blog/?p=27122

41 minutes ago, ARM505 said:

or wtf an EPU is

From Internets: "The emergency power unit (EPU) for the General Dynamics F-16 “Fighting Falcon” aircraft provides electrical and hydraulic power in the event of main engine generator or hydraulic pump failure or an engine-out condition. The unit is powered by main engine bleed air, or by the decomposition products of H-70 fuel (a hydrazine-water mixture), or a combination of both."

[ARM505]

Thanks, and that article made me search to see if those Tac Attack publications are available online; lo and behold, the USAF has graced us with a repository!

https://www.acc.af.mil/Units/ACC-Safety/Magazine-Archive/

Goldmines of hilarious stories and cool reads.

 

I once again appreciate the openness the Pax Americana has graced us with.

[strikeeagle]

On 8/3/2023 at 12:48 AM, ARM505 said:

I need an 'idiots guide to wtf a JFS is'.

I know APU's (use those every day at work), electric start, cartridge start etc, but have never taken the time to get JFS units. So.....what are they? What principle do they work on? Do they really start as fast as depicted in this module? Do they need warmup time? I assume they run on jet fuel? Are they just small APU's (ie. small gas turbines?) Anyway, it looks relatively small at least (I assume it's the thing in the middle of the other two things on the left in the photo - my guess is CGB (central gear box?) then JFS, between two gennies, then the hyd. pumps, and the AMADS on the outside?)

For my next lesson, I'll learn what priniciple of magic an F16 uses to start....or wtf an EPU is....

 

It's a lot to explain, but yes, it starts fast. Starts using stored hydraulic fluid in accumulators under pressure.  Uses a clutch system to accelerate, engage, and spin the AMADS. The F-16 uses a JFS as well, though a different set-up compared to the 15.  More of a direct connect to the 16's accessory drive.

Edited August 4, 2023 by strikeeagle

[jaylw314]

On 8/2/2023 at 10:48 PM, ARM505 said:

I need an 'idiots guide to wtf a JFS is'.

I know APU's (use those every day at work), electric start, cartridge start etc, but have never taken the time to get JFS units. So.....what are they? What principle do they work on? Do they really start as fast as depicted in this module? Do they need warmup time? I assume they run on jet fuel? Are they just small APU's (ie. small gas turbines?) Anyway, it looks relatively small at least (I assume it's the thing in the middle of the other two things on the left in the photo - my guess is CGB (central gear box?) then JFS, between two gennies, then the hyd. pumps, and the AMADS on the outside?)

For my next lesson, I'll learn what priniciple of magic an F16 uses to start....or wtf an EPU is....

 

My understanding is that a JFS only does work through turning the shaft.  It has to be mechanically hooked up to the engine it is starting, and doesn't do anything else.

APU's does other useful stuff, like providing bleed air and electrical power.  

[strikeeagle]

14 hours ago, jaylw314 said:

My understanding is that a JFS only does work through turning the shaft.  It has to be mechanically hooked up to the engine it is starting, and doesn't do anything else.

APU's does other useful stuff, like providing bleed air and electrical power.  

You’re in the ballpark 

[Rainmaker]

16 hours ago, jaylw314 said:

My understanding is that a JFS only does work through turning the shaft.  It has to be mechanically hooked up to the engine it is starting, and doesn't do anything else.

APU's does other useful stuff, like providing bleed air and electrical power.  

It has a small PMG on it, at least on the -15, so it gives you a few small things like intercom, fire detection, and engine engagement selection.  Nothing in terms of what an APU is designed for. 

Edited August 5, 2023 by Rainmaker

[Hatman335]

Salty has already written a great intro text on the basics of the secondary power system, I'll copy it, and he's also drawn a great illustration as well.

 

"The Jet Fuel Starter is jet engine in it of itself. We used stored potential energy in the form of hydraulic fluid and pressurized nitrogen. This gets the JFS started. The JFS has its own electric and fuel requirements completely separate. Once the JFS is started the lubricating oil turns into control oil. This control oil, when prompted by finger lift on the front of each throttle, will put 350psi of oil into the “iso decoupler” we call them “stub shafts”. These extend out and into the “Pawl Carrier” on the AMAD. The pawl carrier is the catchers mitt. Once engaged it begins to rotate and spin the AMAD which has 2 pumpnulls 1 generator and the Power Take Off (PTO) shaft. The PTO connects the AMAD to the engines gear box. This is where your rotation is coming from. Once over 20% you are cleared to go over the hump with the throttle, but I wait untill atleast 24% N2 RPM. The motor will accelerate with the JFS until it reaches 50%-54% which is when the JFS will disengage/shut down depending on if the other motor is already cranked"