Forum: F-16 Procedures

Guest

Does anyone have any data on when the Halon inerting system is activated? I am told that it is only used for ground support missions (bombing raids) but not for high altitude engagements. In other words the halon inerting system is activated only below 10,000 ft. I am studying the effectiveness of the Halon inerting system and any data would be appreciated.

Thanks!

Dan

F-16.net Sponsor

Any crewchief out here who could answer this one?

Good question. Way back in the late 80's and early 90's, I worked block 25's over at Hahn AB in Germany, and we ALWAYS had full halon bottles for every mission. In fact, we had to demonstrate the ability to change the rubber O ring on the QD during our ICT's.

Now I work the same block 25's in the guard, and we NEVER have full halon bottles. We have even delopyed over to PSAB and we did not have full halon bottles.

Does anyone know the answer?

It works anytime there is Halon in the bottle and you select "tank inerting". There is no altitude restriction to its use. Air to Air engagements are just as susceptible to battle damage to the fuel system as Air to Ground.

Is this related to the fuel system layout ??

Yes it is used to inert the fuel vapors that gather at the top of the tank as it emptys, contrary to popular belief it is not used as a fire ext. but rather to prevent fires from occuring.

Wow. Great info. Thanks.

This makes more sense now. Example a jet like an F-15 has an open fuel system it vents excess fuel and vapor a lot. Notice when you see one doing aerobatics that you will see some fuel vent from the wing tips. This is where it dumps fuel when needed also. So different fuel system problems/solutions on different aircraft.

As for the guy with the Block 25s above.... would the move from JP4 to JP8 have anything to do with this? ( big guess on my part, sorry )

O.K. getting way out of my comfort zone. When in doubt, ask a crew chief, or fuels engineer or F-16 depot person. Cool

Interesting topic for sure.

The reason they don't have the Halon bottles full is because of the "unfriendliness" of the halon to the environment. Halon is supposedly an ozone depleting substance. Stateside jets wont have theirs full because there is not much chance of "combat" related fires.

elp,

Quote:

Example a jet like an F-15 has an open fuel system it vents excess fuel and vapor a lot. Notice when you see one doing aerobatics that you will see some fuel vent from the wing tips. This is where it dumps fuel when needed also.

I hate to say it, buy you seeem to be misinformed. The F-15 uses a pressurized fuel system (I dug out my printout of the TO -1F-15A-1 and verified this, sorry it took so long). The tanks are sealed and presurized when the LG handle is selected up. The fuel only dumps from the right wing also.

The vapor trails that you see from the wing tips is actually due to low pressure areas in the vortexs of air tumbling off the ends of the wings. The low pressure causes any vapor in the air to turn to a steam and become visible. I have seen the same off many different aircraft at hot, humid airshows. At the Dayton International Airshow back in about 1985 B-1B #13 arrived doing a 600kt pass and not only was trailing vapor off the wings, but the area under the intakes was also shrouded in clouds. Very impressive.

This is the same mechanism that causes the famous shock wave photos of USN aircraft going supersonic. The reason you don't see the same cones off USAF or other air forces aircraft is because you don't usually see those aircraft supersonic near the surface of the ocean (where the humidity is very high of course). If an F-16 did a low (under 300ft) supersonic run over an ocean in the right conditions you would get a similar view.

Kevin
The Ejection Site

To add to what kmceject wrote, vortices (plural of vortex) are low pressure areas. When pressure drops sufficiently the moisture suspended in the air (humidity) can drop out of suspension and become visible as tiny droplets of water vapor, just like a cloud. When the vortex collapses and pressure rises the water vapor goes back into solution (suspension) in the air and the trail disappears.

Wingtip vortices are frequently seen on F-15s and F/A-18s as well as commercial airliners. I have even seen helix-like vortices streaming from the props of C-130s on takeoff. F-16s are better known for the vortices shed by the forebody strakes as seen in these photos:

http://www.codeonemagazine.com/archives ... mm_14a.jpg

http://www.codeonemagazine.com/archives ... mm_14b.jpg

http://www.codeonemagazine.com/archives ... mm_15a.jpg

This is the same effect as a wingtip vortex, just in a different place.

It is worth mentioning that those F-16 strake vortices are there by design. The vortex, and it's low pressure air volume, is designed to occur over the length of the strake and the wing root body blend. The combination of low pressure and high energy (due to turbulence) in the vortices generates additional lift, helping the F-16 achieve it's phenomenal turn rates.

By comparison any wingtip vortex is essentially lost energy. The winglets (vertical wingtip extensions) you see on many commercial airliners are designed to use this vortex energy to increase lift and lower drag, increasing fuel economy and range.

Sorry for going off the original topic but I thought this info would be useful.

Yes I was misinformed Cool

On one of the many depot mods, one side was closed off for dumping. The jets still vents fuel out of both wing tips (from the surge box). Also like you, I have seen high speed air come off of the surfaces of many aircraft. However, you can in fact see a little wisp of venting out of each wing tip once in a great while (after a slow inverted roll).

Quote:

you can in fact see a little wisp of venting out of each wing tip once in a great while (after a slow inverted roll).

IF your talking about fuel here your SO WRONG. There isn't any fuel coming out of the plane except the vent points. On the 16 its a small hole on the lower middle section of the left wing. On the 15 its the right wing.

No fuel is "wisping" out of the wing tips.

Thanks Dave Wink

elp wrote:

Is this related to the fuel system layout ??

Yes, it is related to the fuel systems layout, the Fuel inerting valve in in the "Vent Box" When activated it will take air from the internal V&P to dipusre the halon, halon is not used in the USAF enless they are in a combat area, last time we went to Turkey we had full bottles, It should only be used for small arms fire damage.

Forum: F-16 Procedures

Halon inerting system/Vortices