Stealth planes can't be seen (very well) on radar. So one stealth plane should be unable to locate another stealth plane on its radar and vice versa.
So how would one stealth plane locate another, friendly, stealth plane?
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asked Apr 25, 2015 at 9:21
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3$\begingroup$ If someone knew the answer, they would not post it here. If they don't know the answer, they will be guessing. Therefore, voting to close. Sorry. $\endgroup$– SimonApr 25, 2015 at 9:46
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44$\begingroup$ @Simon I disagree. Surely stealth technology can be spoken about in general terms without affecting state security. $\endgroup$– BenApr 25, 2015 at 10:55
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3$\begingroup$ @Ben Yes, but then it would be guesswork and therefore of no use. $\endgroup$– SimonApr 25, 2015 at 11:03
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3$\begingroup$ @Simon: Stealth can only be maintained when no radiation is emitted. Radar is not an option, and the premise of the question is wrong. $\endgroup$– Peter KämpfApr 25, 2015 at 12:33
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35$\begingroup$ @Simon You seem to be assuming that there is zero public information about stealth aircraft. This is not at all true. There's plenty of scope for non-speculative answers. $\endgroup$– David RicherbyApr 25, 2015 at 15:46
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5 Answers
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The accounts that have been published of F-117 missions indicate that they generally flew single-ship, rather than formation missions, and it seems probable that B-2 aircraft do likewise. So in a sense, the important question for those aircraft isn't "how do I know where (another stealth aircraft operating nearby) IS," but "how do I ensure that we don't collide with each other," and that's a much easier question.
There are several ways to "deconflict" multiple aircraft operating in relatively close proximity that don't involve seeing or painting each other on radar. One aircraft operates at one altitude, another operates at a different altitude is one method, while timing over a point (you get to waypoint ABC no later than 19:00:00, and I'll be there no sooner than 19:00:30) is another, and physical separation (you stay west of this longitude line, I stay east) is another. In practice, all of these can be combined to ensure that "your" mission is deconflicted from "my" mission.
Of note, it isn't only stealth aircraft that will use tactics like this. Helicopters operating blacked out at night don't have air-to-air radar, and even with NVG's, the ability to see each other isn't reliable enough to plan on "see and avoid" and the "big sky theory" to preclude a mid-air, so they'll use some fairly detailed deconfliction plans incorporating separation in space and time.
More recent stealth aircraft such as the F-22 and F-35 are reported to have datalink capabilities so that they can "see" each other without radar, by means of an encrypted, stealthy broadcast of each aircraft's position and track. This would allow multiple aircraft to fly in formation (not close formation, but perhaps 1000' or more apart), and to work with other aircraft equipped with the same datalink, so even though the bad guys would only be able to see the non-stealth aircraft on radar, the friendlies could all see each other.
answered Apr 25, 2015 at 12:12
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3$\begingroup$ From the book "Skunk Works": the technology now exists to preprogram computerized combat missions so that our stealth fighters could fly by computer program precisely to their targets (end quote). It sounds like the routes can be set in advance to prevent airspace conflicts. $\endgroup$– David WApr 25, 2015 at 16:13
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10$\begingroup$ The disadvantage of datalink is that passive radar is a thing. The stealth aircraft also needs to limit it's broadcasting, otherwise the enemy could detect it by simply listening. Even if they are unable to decipher the data, the transmitter can be located with directional antennas and frequency and characteristic patterns can be used to identify the side and guess the type. $\endgroup$ Apr 25, 2015 at 19:35
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3$\begingroup$ I know from the methodology of wireless trilateration you need a LOT of signals to determine position with any accuracy, and a very finely-calibrated set of receivers, not to mention knowledge of the broadcast antenna so you know its propagation pattern. The simple "datalink" packets described might show up but be virtually impossible to pin down, especially if they're traveling at high speed when they emit them. At best you could get a very general idea of what region they're in. $\endgroup$– thanbyApr 27, 2015 at 11:57
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7$\begingroup$ @DavidW: That is precisely how the Serbs managed to shoot down one F-117. It flew the same, pre-planned route every day, and they figured out the pattern quite quickly. All they needed to do the next day was to point their guns at the right spot in the sky and fire at just the right time. $\endgroup$ May 8, 2015 at 15:59
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4$\begingroup$ @JanHudec - Spread spectrum transmission can help here; if the datalink transmits in parallel on many different frequencies, you can reduce transmission power, increase fault-tolerance of the encoding to compensate for noise, and end up with the same data rate at much lower power especially on any specific frequency that a passive sensor might be tuned to. This can be combined with EW measures such as having a Growler literally run "interference", jamming the listening stations with broad-spectrum radio noise while the stealth craft are operating. $\endgroup$– KeithSJul 14, 2015 at 20:21
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To not be detected, it is essential to suppress any radiation coming from the stealth airplane. Therefore, radar is not an option and only passive sensing is possible. When stealth aircraft fly in formation, they keep visual contact and avoid IMC flight.
To enable ship-to-ship communication, the F-117 has an optical datalink which uses red laser light to transmit the pilot's voice to another F-117 flying nearby.
answered Apr 25, 2015 at 13:31
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12$\begingroup$ Is it not possible to transmit low power spread-spectrum RF, that looks like background noise unless you have the key to tell you where and when to look? It seems like there should be a compromise to give up a bit of stealth in order to communicate, but still be stealthier than conventional craft (because it's still hard for an enemy to detect that you're an active transmitter and not noise). $\endgroup$– cpastApr 25, 2015 at 17:20
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18$\begingroup$ @cpast: You are correct, and that is the thinking behind the Multifunctional Advanced Data Link. The laser link was chosen as the most stealthy and least likely to be disrupted solution, but spread spectrum links are stealthy enough. $\endgroup$ Apr 25, 2015 at 17:33
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$\begingroup$ How does the plane know where to aim the laser for the datalink transmission? Does it acquire the point of aim visually? $\endgroup$ Nov 19, 2020 at 12:41
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There is no optical datalink over laser for F-117 pilot communications. Comms on that plane was my primary job and I can assure the readers it had no such thing.
The comment about single ships was about right - we had pre-programmed routes and due to autopilot and autothrottle the goal was to keep the airplane on route on time. The comms antenna were extendable, but during combat ops in foreign territory there were retracted and completely shut off all comms.
The idea of skin mounted antennas started to come around but it had not been implemented by the time I left late in 1996. For the OCIP III ring laser INS with GPS sync it was implemented on the backbone of the plane.
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5$\begingroup$ You can turn this into a good answer by just addressing the "how" in the question, and making whatever points you feel need to be made. It is also correct to qualify an answer (by addressing only one model) since not all "stealth" aircraft are alike in their stealth. (F-117 is a different generation of stealth, as you are more keenly aware than most). Glad to see a Stinkbug guy here, welcome! :-) No need to address any of the other answers. Each answer is "supposed" to stand on its own, in the SE method. $\endgroup$ Oct 8, 2016 at 3:06
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The simple answer is that the primary communication is visual when communicating plane to plane. That is established and is part of the ops protocol. To be clear however, normally stealth missions are not flown in a conventional formation.
Aircraft such as the B-2 employ from sat transceivers, datalink and even VLF. Transmit capability is in place for most bands, except to my knowledge not for VLF.
It is not well known whether stealth aircraft have been operationally deployed with metastatic radar, but such radar constellations have been developed for battlefield use. They are effective against low observable targets. A passive metastatic receiver could be deployed on an aircraft such as the B-2.
What is known is that a variety of optical com methods have been employed to permit plane to plane direct communications, at distances of less than 20nm. At first these relied on incoherent sources, but several systems have been tested using coherent sources and tested for data and voice. One such system was employed operationally configured to handle voice. There has been no recent open literature that I have seen recently which would indicate the deployment and operational reliance on those systems.
BTW, selection of the laser frequencies can be done to limit the intercept range of optical communication. For example, using a frequency absorbed by methane can create a good signal to noise at altitude, and the attenuation gets greater closer to the ground. The effect is two-fold as the emissions are absorbed at altitude (enroute) but the attenuation is much greater at lower altitudes where methane is more abundant.
There are open briefings which reference plane to plane optical (laser) com being used during the enroute phase of what are normally long aircraft missions.
Mission separation strategy is spatial and temporal, and that doctrine has not changed. Temporal separations of less then two minutes have been openly documented.
To summarize, assuming a given phase of a sortie is flown in a stealth mode, it is not possible to utilize "radar" in the sense that the stealth's aircraft radar transmits and receives it's own transmitted returns. To do so would reveal the aircraft's location. However, metastatic radar techniques could allow passive reception of other radar transmitters, and a situational rendering. In absence of that capability, the likely scenario is that datalink from other aircraft, such as AWACs, would provide battlefield awareness, and additional metadata to identify friendly aircraft. Even with metastatic radar, there is not ability to be completely autonomous.
When sorties are convergent, visual identification and separation techniques are used.
Finally coherent optical com are available on some aircraft for plane to plane communication.
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One technique which is available to many military planes in radio (incl. radar) blackout is formation lights and markings.
Reference the thee images below of F-15 aircraft. Note that in the image made from slightly above the aircraft there is a clearly visible bright rectangle below the pilot and directly in front of the intake ramp. In the image made nearly level with the aircraft the rectangle is dull and only slightly apparent. In the image made from below the aircraft, this marking is almost indistinguishable from the area around it.
http://www.airforce-technology.com/wp-content/uploads/sites/4/2017/09/eagle2.jpg
https://i2.wp.com/www.defensemedianetwork.com/wp-content/uploads/2012/07/F15C-Eagle-Takeoff.jpg
http://enacademic.com/pictures/enwiki/84/Two_JASDF_F-15J_take_off_in_formation.JPEG
More modern systems can also make use of markings and cameras which reflect and detect exclusively outside the range of human vision, similar to the way a self driving car can track those around it. Formation lights can be used instead of markings and are especially useful when flight crews are equipped with night vision systems.
To my knowledge, formation markers are used more readily by non-stealth aircraft operating in clandestine capacities. Night penetration missions for special forces helicopters, for example, require that the aircraft fly very close together in a "blacked out" state. In fact, stealth planes like B-2's will be spaced out by flight planning and careful monitoring of autopilot and GPS and therefore never need to locate or avoid each other.
Although Formation markings and lights aren't likely to be frequently used by stealth aircraft pilots, the OP asked specifically how those pilots would locate each other (which is unlikely) rather than how they avoid the need to locate each other (which is more realistic.)