Forum: F-16 Procedures

Always been curious if you have to add ballast to the jet when the engine is pulled to keep it from tipping and if so, where and how much.

Thanks

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No, but sometimes you will see a brace installed when the engine is pulled. I have never seen a jet nose forward, the bigger fear (IMO) is pulling too much out of the front and having her lean back. Not sure what the regs are anymore, but I know if you pulled the radar package and the seat you started having issues with the CG shifting too far aft.

Enthusiast Joined: Sep 26, 2006 - 10:26 PM Posts: 55

nam11b wrote:

No, but sometimes you will see a brace installed when the engine is pulled. I have never seen a jet nose forward, the bigger fear (IMO) is pulling too much out of the front and having her lean back. Not sure what the regs are anymore, but I know if you pulled the radar package and the seat you started having issues with the CG shifting too far aft.

Not too much worry about fwd heavy CG but we do install the nose jack pad and hang a concrete block off of it if we have aft heavy CG. That one you gotta worry about, especially if dudes are crawling around on the backbone! Surprised

T.O. says to seat some jacks on the mains if certain components are removed.

LinkF16SimDude wrote:

Always been curious if you have to add ballast to the jet when the engine is pulled to keep it from tipping and if so, where and how much.

Not so much a tipping hazard, but if the engine is removed and there isn't enough weight in the aircraft as a whole, it will 'rise' too much on the gear struts.

There is a minimum 'weight' / 'height' in the technical data that needs to be addressed prior to removing or installing the engine.

Say the gun is removed, radar removed, as are the seat and canopy, then the aircraft has been completely de-fueled and the wing tanks removed. The aircraft will 'rise' so much on the gear that the standard engine R&I (Removal & Installation) trailer can not attain the proper height to safely remove the engine.

When removing the engine on later block Vipers there is a specific height above ground that the rear fuselage must be positioned. This is why we use the jack under the nose; raising the nose so that the aft end (Motor end) is at the proper height for the trailer. There are also limits on how 'high' you can 'position' the nose. (Measuring nose strut extension) If the limit is exceeded you are no longer 'positioning the aircraft' but now 'jacking the aircraft' and new limitations fall into place. (Amount of stress panels installed, number of jacks, etc)

If the aircraft is too light, you can get the engine 'stuck' so to speak. While removing the last of it's weight from the aircraft, the aircraft will begin to rise, at the same time you reach the end of the R&I trailer's maximum extension. What you end up with is weight still on the forward engine mount, but no way to pick it up more with the trailer. (Bad situation) The back of the engine is firmly on the trailer, but the front of the engine is still 'hanging' from the aircraft. At this point you hope adding a little air to the trailer tires is enough to free the engine! Whistle

So to answer your question in plain terms; no "ballast" is not used when the engine is removed, but proper weight/height must be maintained by the installed equipment and fuel loads in combination with a nose jack for proper aircraft positioning.

On the other hand I've seen Vipers want to 'tip up' when too much is removed from the nose end while the engine is still installed. Again it's more of a weight issue. When too much weight is removed from the nose (Hopefully prior to this point) a single jack is installed at a rear point to act 'prop' so that the aircraft doesn't tip.

Keep 'em flyin' Thumb

TEG

There are jacking, towing and hoisting limits in the 1F-16( )-5-2 that also must be looked into prior to transitioning the aircraft. Your friendly Weight and Balance QA person can run a quick scenerio with components removed, state of fuel, configuration, etc. to give you a quick and accurate weight vs. CG on your aircraft.

I saw it once back in '82 or so at Hill. A block 10 A model in the hangar, engine still in but gun, seat & canopy removed along with various avionics stuff. Some poor A-shopper took out one more box, put it on the hangar floor and when he turned around to close the panel the jet was rotated as if for takeoff. An unfortunately placed drip pan crunched one ventral fin, otherwise nothing was damaged but egos. The 421st guys got pretty tired of the rest of us driving by and laughing...

Forum: F-16 Procedures

Ballasting