24
$\begingroup$

I've been wondering this for quite a while: Why do the missiles on the F-16 point down a little bit?

See how they point down?

I went and did a little searching and found out that the F-16 isn't the only plane that has this feature, so I'm going assume it's not the F-16s frame specifically. I also doubt it's tactical because all the weapons are pointing down, regardless of the weapons role in combat. In fact I saw a few photos where the bombs closest to the fuselage were pretty level with the ground (and bombs pretty much always go down, so...)

Does it have to do with aerodynamics, or perhaps ease of loading? Why is the load-out on the F-16 mostly pointed slightly downwards?

|improve this question
$\endgroup$
  • 3
    $\begingroup$ Just a thought: During level flight the plane itself will point slightly upwards. Would this be enough to make the missiles horizontal at that point? $\endgroup$ – collector Jun 12 '15 at 23:00
  • $\begingroup$ My guess would be aerodynamics, such as geometric twist or something like that. $\endgroup$ – SSumner Jun 12 '15 at 23:37
  • 3
    $\begingroup$ Well you probably don't want them pointing slightly up, do you? $\endgroup$ – Brian Drummond Jun 13 '15 at 19:26
24
$\begingroup$

If you take a look at the picture again, you'll see that the missiles are in fact lined up quite nicely with the nose of the plane. The missiles are not pointed down, they are pointed forward. The wings and engine (and the entire back two-thirds of the plane) are pointed up, which provides the lift to keep the plane in the air during normal flight. You can see pretty well the alignment in reference to the horizon in this picture (found by @jay-carr):

Image of F16 showing nose and mounted missiles pointed at the horizon.

Just to cut off the potential comments about how planes generate lift, reference is here.

|improve this answer
$\endgroup$
  • $\begingroup$ I think a lot of people here are actually familiar with how airplanes actually generate lift (in fact I suspected this may be the actual reason.) If you could explain it a bit here though (for anyone who isn't aware), and how it relates the mounting of the weapons here, that'd be nice :). $\endgroup$ – Jay Carr Jun 13 '15 at 4:02
  • 7
    $\begingroup$ @JayCarr that's not true for the Rhino, 250 vice 350 makes a large difference in nose position. And anyway, as a guy that flies the Rhino, I'm telling you that the main reason our ordinance is hung in the manner it is, is to mitigate midair collisions during jettisons. I doubt the viper is dissimilar in that respect. I have no doubt that secondary considerations revolve around efficiency though, but efficiency doesn't trump safety--that's why the Rhino is such a pig. $\endgroup$ – Rhino Driver Jun 13 '15 at 4:33
  • 2
    $\begingroup$ @RhinoDriver - Hmmmm...... You make a very good point, and I'm not about to argue with an actual F-18 pilot... So instead I've written Lockheed and I'm going to see what they say (if they even respond). If they don't, I'll probably just watch the vote count and see what the community says. $\endgroup$ – Jay Carr Jun 13 '15 at 4:47
  • 4
    $\begingroup$ @JayCarr If you can get an actual answer from Lockheed I'd love to hear it. I'm pretty curious about it myself. That's the info we've been fed. If its for a different reason, I'd love to know. $\endgroup$ – Rhino Driver Jun 13 '15 at 22:46
  • 1
    $\begingroup$ This answer is very plausible but te picture actually demonstrates very little. It's very hard to tell whether the photograph is straight, since the literal horizon is mountainous and the features on the ground are too small to determine where true vertical is. (And, if the camera isn't pointing absolutely level, perspective will make the verticals in the frame lean in or out except very close to the centreline.) $\endgroup$ – David Richerby Jun 14 '15 at 11:44
14
$\begingroup$

Usually stores are hung off an aircraft in such a manner to facilitate a safe auxiliary free-fall release. The AUX release is used if the CAD misfires and the stores cannot be physically ejected downward away from the aircraft. Although this wouldn't really apply to the wingtip loaded aim 9's, so I can't really account for those. In the super hornet the pylons are canted outwards for just this reason.

In fact, the emergency jettison doesn't even release the wingtip aim 9's because, in the case of the Rhino, the wing is more efficient with them in place. The wingtip 9's act as a winglet of sorts.

|improve this answer
$\endgroup$
  • 1
    $\begingroup$ And CAD is...? (I can guess from context, but what's it stand for?) $\endgroup$ – cpast Jun 13 '15 at 1:37
  • 1
    $\begingroup$ @cpast For the life of me I can't remember what it stands for, but its a small explosive charge. It's been described to me akin to a shotgun blast. $\endgroup$ – Rhino Driver Jun 13 '15 at 1:43
  • 7
    $\begingroup$ Cartridge Actuated Device. $\endgroup$ – Todd Wilcox Jun 13 '15 at 3:02
  • 1
    $\begingroup$ @JayCarr There are no stores inline with the intakes of any aircraft I'm aware of. You'd be right to assume that'd be very dangerous. To answer your question, yes, it probably makes a great deal of difference. Even more so, the small cant adds a tremendous amount of drag, this is especially exacerbated in the Rhino which is also canted outwards. $\endgroup$ – Rhino Driver Jun 13 '15 at 4:11
  • 1
    $\begingroup$ I can't speak to the F-18 obviously, but I assume it's similar to the -16. I'm not sure exactly if this was part of the design for the Viper. Anyway, you can't jettison any of the air-to-air stores, not just just the wingtips. Additionally, and I assume the Hornet has the same design, but the computer runs through some logic to figure out if it needs to delay dropping certain stations to prevent collisions. $\endgroup$ – user3309 Jun 13 '15 at 17:56
6
$\begingroup$

It's not just the wingtip launchers that are canted downwards. All pylons are canted downwards a couple degrees (~2 I believe). This is to reduce the AOA to 0, thus reducing induced drag at pickle. There might be more to it in terms of aerodynamics, but I didn't engineer the jet.

|improve this answer
$\endgroup$
  • 2
    $\begingroup$ Usually the AOA is not equal to zero. Also for commercial airlines the fuselage is not at 0 degrees. Since it is also possible to generate lift using these bodies (rockets or fuselages) you want to have them at the angle that maximizes lift/drag. $\endgroup$ – ROIMaison Jun 15 '15 at 15:03
  • $\begingroup$ @ROIMaison do you have some source? In the F-16, the AOA is roughly ~2 degrees at 350-450 knots. With the pylons canted downwards ~2 degrees, the AOA should (according to my math) be 0 degrees AOA. You're comparing the fuselage of an airliner to that of a missile... They aren't the same. $\endgroup$ – user3309 Jun 15 '15 at 22:39
  • $\begingroup$ I don't really have a source, I just applied the same logic used on the fuselage to the positioning of rockets. You're right that the two aren't the same, and maybe the size of the rockets is too small to generate any significant lift. $\endgroup$ – ROIMaison Jun 16 '15 at 6:55
  • $\begingroup$ I don't know why but I didn't see your answer when this question was more active. It looks like you're confirming what Samuel Scheiderich suspected though, and I figure you would probably know... His question is voted a bit higher though, hence I accepted his as the answer. Yet another situation where I wish I could mark multiples as correct... $\endgroup$ – Jay Carr Aug 14 '15 at 17:42
  • 1
    $\begingroup$ @PeterKämpf The Wikipedia article doesn't indicate that it has entered service yet. Some academics messed that up? $\endgroup$ – user7241 Dec 10 '17 at 10:23
4
$\begingroup$

A related reason is ensuring safe store separation.

A lot of testing is done to ensure your munitions and fuel tanks don't come back to greet you.

So this doesn't happen: YouTube video of 'Aircraft Store Separation Incidents'.

The B-1 bomber had a similar issue initially where weapons would not exit the bomb bays and just skip along on the laminar flow underneath the aircraft. They had to add these spoilers to the fronts of the bays to break up the airflow. The spoiler is the waffle iron looking plate in the front. It drops down when the bay is opened for weapon release. http://miramar.airshowjournal.com/2005/IMG_0327_2.jpg - philosoguido - https://www.reddit.com/user/philosoguido

The B-2 has similar waffles.

|improve this answer
$\endgroup$
2
$\begingroup$

Not sure about the AIM-9, but the AIM-120 is mounted 6 degrees down from F-16 bore axis. That means that from the pilots point of view its seeker view is centered in the middle of the HUD (below the bore-sight cross which is in upper part of the HUD). That might also be part of the reason for that alignment; to make it more convenient for the pilot to aim when shooting in BORE mode.

|improve this answer
$\endgroup$
0
$\begingroup$

I believe it's a bit of washout in the wing. Washout is a slight twist to the wing, reducing the angle of incidence at the tip and reducing the probability of tip stall.

|improve this answer
$\endgroup$
  • $\begingroup$ Downvoter: If this answer is not correct, please fix the linked Wikipedia article, including the photo caption. $\endgroup$ – Fred Larson Jun 15 '15 at 15:15
  • 1
    $\begingroup$ It's incorrect because it has nothing to do with washout. The weapon is mounted such as to be horizontal when the aircraft is flying straight and level, which means it's flying with a slight nose-up attitude which translates into a slight angle of the wing as well. $\endgroup$ – jwenting May 1 '19 at 5:24
-5
$\begingroup$

Its so that the thing goes down (and away) from the aircraft when it is released.

For example, imagine the missile was canted up instead of down. Due to aerodynamics it might fly into the wing it was released. The armament is canted downward to prevent this.

|improve this answer
$\endgroup$
  • 2
    $\begingroup$ Your scenario is not possible, the missile fires off of a rail and already has tremendous forward momentum when it leaves the aircraft. $\endgroup$ – Rhino Driver Jun 13 '15 at 0:44
  • $\begingroup$ @RhinoDriver All ordnance is canted down, whether it is self-propelled or not. You cannot assume that the engine of a missile will operate correctly every time. $\endgroup$ – Tyler Durden Jun 13 '15 at 0:52
  • 1
    $\begingroup$ Let us continue this discussion in chat. I left my initial comment as a primer, but I moved subsequent comments to chat. $\endgroup$ – Rhino Driver Jun 13 '15 at 2:10
  • $\begingroup$ No, just no. You need to read up on AMRAAM trajectories. You'll find that it has a large upward trajectory. $\endgroup$ – user3309 Jun 13 '15 at 17:34
  • $\begingroup$ @TUMBLEWEED that is if the engine fires $\endgroup$ – user7241 Dec 10 '17 at 9:15

Not the answer you're looking for? Browse other questions tagged or ask your own question.