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every aspiring carrier pilot must de- the ■2nC* ma'nta'n proficiency in flying v'sual carrier landing system to be-
corne
of
(a qualified tailhooker. The number
e°mbat-ready carrier pilots available is
tfectly related to the pilots’ abilities to
ster the visual system. But is the cur-
si v'sual carrier landing system (con-
tlng of the ball, datums, deck lighting or st- . ’ ° °
tll(jp , - -
ke .and angle of attack instruments) eePtng too many good pilots off the u“cks i the
Th,
striping, drop lights, and aircraft atti-
fnnecessarily, thus contributing to ^ shortage of fleet carrier pilots today? I Tu3nsvver *s yes’ anc^ here’s why
Ue P11 fro n t tiionnl eirnfntvi ir 11
anyth;
ducti
tiust
e current visual system is unlike
dy nin8 a pilot has seen prior to its intro- ct'on in flight training. Thus, a pilot
’istruc
tioi
ions- tu i
*ion me ens on tdc lineup informa- attit dlrcct|y ahead; and airspeed and c°ck 6 'n^ormat*on either inside the the k^11 or Peripherally with reference to in °r*zon. Plying the ball is so demand's at even a short break in tempo (such to L°rt call) requires a warmup period rC(j^et hack up to speed. If the period of de ,Ced operations is longer, as between is v’ ^rtlents’ the needed workup period ca .al'y as intensive as any previous ^ Qler qualification.
hire r.v‘sual system is deductive in na- 'v'th respect to two variables, verti
cal
are
^ SLeed indication and drift rate, which devCrUical t0 a phot in avoiding large ba]]latl°ns and overcorrections. While the Slid te" a Pdot where he is on the tifhe-P6’ d must he scanned several c°mh ln successi°n, then integrated and rrf0vlned with his last stick and throttle
goin
cnients to determine where he is
llarly,
8 to be in the next few seconds. Sim-
ln the horizontal problem, one
glance will tell the pilot if he is left or right, but figuring out where he is going involves remembering the last couple of peeks as well.
► Dispersed information sources and the lack of an artificial attitude reference other than the aircraft’s own instruments contribute to the danger of losing situational awareness. When recognized by the pilot or brought to his attention by the landing signal officer (LSO), recovery may mean a bolter or waveoff and the attendant decrease in boarding rate. If the pilot fails to respond, or does so inappropriately, the result can be tragic.
would remain, and, therefore, the basic proficiency levels and notional performance results would not improve very significantly.
While the present system has been an old friend of tailhookers, serving well for many years, a better way to get on board that will bring about a quantum improvement in fleet safety and readiness may be on the horizon.
The New Carrier Landing System (NCLS), also called “Nickels,” which the author began developing in 1986, is one proposal now under review (officially submitted as a proposed Tentative
These deficiencies are inherent characteristics of the present system. Further refinements or add-ons, such as vertical speed indication bars on the lens and horizontal position lights on the ramp could produce incremental improvements in the fleet, but they would also become additional items to be scanned and interpreted. The fundamental shortcomings
For years, flying the ball has been the best way to guide aircraft on board the carriers. “Nickels” may offer a new way to get more good pilots carrier qualified, and an easier way to keep them qualified.
Operational Requirement by Attack Squadron 36 at Naval Air Station, Oceana Virginia.)1
NCLS was designed as a one-for-one replacement of the current visual system and included items that a pilot might have on a “shopping list” of desirable characteristics for a new system. The replacement criteria were that NCLS should:
► Be ship-based
► Allow only low-probability-of-inter- cept emissions
► Have no data link
► Have no ultra high frequency transmissions (normal “ball” call desirable, but not required)
► Require no electrical power from the aircraft
► Be operable in at least the same visibility conditions as the current system
► Be capable of indicating flight path position with at least the same precision as the current system
► Be able to compensate for ship motion (pitch, roll, and heave)
► Retain the monitoring, assisting, and waveoff roles of the LSO
Items on the “shopping list” asked that NCLS:
► Provide the pilot with integrated precision symbology that permits direct sensation of all the necessary variables of a carrier approach in one presentation, encompassing: glideslope position; vertical speed relative to the glideslope; lineup position; drift rate; airspeed relative to optimum; and aircraft attitude
► Keep the display simple, uncluttered, and straight in front of the pilot
► Convey situational awareness to the pilot so that he knows immediately what is happening just by looking at the display and is able to apply the proper correction naturally
► Base the display on universal skills, such as ordinary navigation (as found in maintaining the centerline of a street or, in three-dimensional terms, negotiating one’s head through the passageways, hatches, and ladders of a ship).
► Incorporate computerized grading into the system, and make it available instantly to the LSO for on-line reference, then later in printout form for debrief, and in periodic (for example, monthly) summaries showing cumulative trends for each pilot.
A representation of the NCLS display in Figure 1 shows an F/A-18 Hornet pilot looking at a real-time, high-fidelity 3-D holographic image, consisting of a series of projected boxes. These boxes form a tunnel toward the deck of the carrier. The axis of this tunnel is aligned with the desired eyepath of the pilot; that is, if he sees himself stabilized in the center of the tunnel, then his tailhook is on the correct path to engage the targeted arresting cable. The pilot flies down the tunnel, keeping the presentation symmetrical, until the aircraft touches down. The tunnel display remains directly ahead right up to touchdown, so he need not turn his head or refocus during the final approach.
As simple as the Nickels display appears, it still conveys the six approach variables listed previously. Perfect “on- and-on” flight is achieved when the boxes are concentric (Figure 2a). A small dot appears at the center of the display and is only visible when the pilot’s eye is on the tunnel axis. The pilot perceives lineup and glideslope deviations whenever the tunnel presentation appears asymmetrical.
The nearest (largest) box is the pilot’s “fly to” box. When the boxes begin to “bunch up” along one side or into a corner of the tunnel (Figure 2b), the pilot knows he’s slightly off glidepath.[1] For larger deviations, the tunnel is further skewed (Figure 2c). When a deviation becomes very large, one side of each of the interior boxes is masked off (Figure 2d), obviating a large correction. (Masking also prevents an optical illusion of image inversion caused by crossing lines.) Gross deviations beyond the limits for a safe correction cause the tunnel to disappear. This discourages “big plays” for the tunnel from outside safe parameters. For an LSO-initiated waveoff, the presentation can be turned off with the waveoff pickle switch and replaced with a waveoff command display.
fushii
and ert’ca* sPecd relative to the glideslope horizontal drift rate information are het Ve^e<^ hy the rate of change of spacing ween the edges of the tunnel box ele- lineents- Thus> as the aircraft drifts left, the th ef- °n s'^e w'h converge while
. hnes on the right side will diverge; the left W*" have the sensation of moving as Well as being left of center, irspeed information is displayed by a
tion. if
°oxes
incj.ltch and roll attitude information is tunne* stability. The tunnel "'ith Urt*lest ahead of the aircraft is stable droresPect to the horizon, and will thus v,e^ the aircraft pitches up and vice Pilot* ^°r 3 P'tch down. Similarly, the hank rea<Jily discern an angle of
°f th ’ kased on the horizontal orientation SUrfae ^’splay, which parallels the earth’s tkeCe' ,^s before, if the pilot exceeds r0u maximum safe limits for pitch and ^ the tunnel display will turn off.
Nc, ^hematic of the primary elements of °pe ,'s shown in Figure 3. To begin the try sequence, all relative geome-
ti0n . aircraft (range, azimuth, eleva- spec’Station, and velocity) with reshin t0 S^‘P’ usmg passive,
Systm°Unteti Ship’s Inertial Navigation sense‘? ^SINS)-stabilized equipment is Sens h an<^ combined with known, typge ’ 0r assumed data on wind, aircraft The ’ ®ross weight, and configuration, hies 8e°metry solver collates these varia- determines functional relative and thtr^ between the aircraft, the ship, appro6 earth. From this information, the see Priate image that the pilot should Toa.n be selected from a library. vergelsP'ay the image, a nominally di- airr>ed ’ Var'able frequency laser beam is at the aircraft, striking a holographic plate in the pilot’s forward field of view. This makes visible one of many holograms stored in the plate. Figure 4 shows some possible unobstructed locations for the geometry sensors and the stabilized laser-aiming platform, as well as alternate laser locations to be used in the event the primary platform is dam-
;tify
the
► Higher carrier qualification rates in
play that intuitively represents the pr°
rob'
► Reduced workup requirements for,6 ^
steeper learning curve and more shad0''!
approach is much more demanding
:ed ifl
and have a greater mental reserve, a-
.ll°'r
ing him to apply additional concentra^
cyclic deck motion. Adding this precision to the timing problem that the LSO currently resolves mentally, the tunnel presentation can be so finely adjusted that the aircraft flight path will be exactly in phase with deck motion at touchdown. A refinement would be to include the pilot himself in this adjustment loop. Each pilot would be “fingerprinted” by recording his reaction times and the sizes of his corrections to tunnel deviations. Then, in poor weather or during a series of bolter passes, the NCLS display can be phase- and amplitude-adjusted to account for a pilot’s individual tendencies.
There is no technological breakthrough needed to make NCLS a reality. Passive sensors, real-time computer software, tunable lasers, and transmission holograms are already in use in other applications. Use of these elements in the NCLS is an adaptive consideration. NCLS does, however, require an extrapolation of current estimates of the total number of holograms that can be stored in a single plate. As the number of holograms is increased, the plate becomes thicker, and the increased range of laser frequencies needed creates a color range in the display (from, say, bluish to greenish). Also, a high degree of precision and stabilization is necessary to initially generate a crisp holographic image; this compounds the manufacturing process when many holograms are to be stored together, and would probably require development of new manufacturing techniques. The best speculative estimate of the maximum number of images that can be stored in one plate is about 1,000.2 Depending on the number of images required to retain motion continuity, the total number of images necessary for NCLS could run into the tens of thousands.
For the capabilities it would deliver, NCLS is not an expensive system.Virtually all of the hardware is obtainable off-the-shelf. The two major costs are in research and development to produce the holographic plate (the unit cost for each plate should be relatively low, since the same set of images is used in every aircraft; it is merely necessary to crop those plates that will be used in smaller cockpits), and the testing and evaluation of the system. Since NCLS is not an upgrade of an existing system, a significant amount of field testing and refinement would be necessary to achieve the confidence level necessary to approve replacement of the current visual landing system.
How soon NCLS can be in place will depend on the support given to the project and the results of a feasibility study. Nearly all the technology and hardware necessary to launch the study are available today.
The primary areas of concern for the reliability of NCLS lie in the sensing and imaging elements and their operation in the wide range of environmental conditions to be encountered. Since the large number of holograms requires a close packing of discrete laser frequencies, a high degree of angular accuracy is necessary to avoid bleed-through of images associated with adjacent frequencies. The incident laser impingement angle is very critical, so the orientation of the aircraft relative to the ship is the most exacting raw geometric requirement.
The laser beam itself may have trouble penetrating a hazy or humid atmosphere. But properly selecting the laser’s operating power and frequency band should mitigate these effects. Lastly, normal vibrations of the aircraft and ship may affect the quality of the holographic image created for the pilot. Damped or fully isolated mounts might be required for the laser platform and the holographic plate.
Accepting NCLS as the primary means of visual recovery on board the aircraft carrier has several prerequisites. First, of course, it should be emphasized that in electromagnetic radiation emission control conditions, a visual recovery is still the only way to land on the ship. Next, it
must be acknowledged that the la1?6 amount of time, money, and manpo"er now being expended using the lens sys tern to train the Navy’s carrier pilots an to maintain adequate levels of fleet safe1) and readiness is due in large part to inher ent shortcomings of that system. DeCI sion makers must be convinced that thn*e operational cost and performance feve can be and must be improved, and tn* the commitment to seek, develop, an install a new system. Most important!)' pilots themselves must believe that there is a better, safer way to trap on board tn ship, and that NCLS embodies the kin of system they would want.
The potential benefits that could 06 gained by developing a new visual earn landing system include the following1
Training Command and the Fleet Reset'6 Squadron (FRS). Presented with a d>s
lem at hand (flying down a narrow1”-" tunnel of airspace), the pilot in train11’' could more readily adapt the ordin”” navigation skills and experiences that brings with him to the Training Con1 mand to developing a successful can-1 approach technique. The resultant hig° ^ percentage of first-time qualifiers wo” increase student flow toward fleet se^ vice. The lower attrition and reduction1 second-and third-attempt training W°u j lower the dollar cost per aviator delivere to the fleet.
rier qualification in the FRS, as wed during fleet refresher training. With
“forgetting” curve, such a system wolL require fewer flights dedicated to in’11^ and refresher training, particularly
ni8ht- . 0.
► Fewer hours required to maintain P ficiency levels at sea. Using more de°P rooted skills and flying a less ment”^ taxing display, the seasoned fleet P1^. would be able to maintain a high Pr° ^ ciency level at sea with fewer hours practice. As a side benefit, this w°u allow greater scheduling flex'd’^', around port calls and shipboard duty quirements.
► Higher boarding (successful alT
ment) rates at night. The night cad”
tn^ its daytime counterpart. But if pla°e ,^gl an intuitive flying environment, the P^ would process information more rap1 •
Ltio“
at night that may not now be avails ^ ► Fewer mishaps attributable to a l08^ situational awareness. Assuming
s°nie mishaps occur because of a satura- °n °f mental faculties in an environment reduced visual cues, it can be expected at these incidents would be reduced if ^ J°ts had all the necessary information in 0rmat that is easily understood. More- ®^er, a display that is more representative 'he current situation and developing nds than is now available would trigger e Pilot’s internal alarm sooner, perhaps r°viding him the additional moments ^eded to effect a safe recovery or make Section decision while still within the
safe seat-firing envelope.
The New Carrier Landing System will not fly the plane for the pilot—carrier landings will always demand the very best flying skills. But the system will tell the pilot where he is, where he is going, and where he ought to be, in a display that is simple, intuitive, and complete. That will allow the pilot to more successfully apply his abilities, resulting in safer, more consistent carrier passes.
The bottom line is readiness and safety, and every nickel or nugget saved
earns a “Nickels” praise.
'Commanding Officer, Attack Squadron 36 letter 13800, Scr 00/023, dated 18 March 1987. 'Obtained from Drs. Ray Patten and Jerry Blodgett. Applied Optics Branch. Naval Research Laboratory. Washington, D. C.
Lieutenant Jenista received B.S. and M.S. degrees in aerospace engineering from the University of Notre Dame in 1981 and 1983, respectively. He received his pilot wings in June 1985 and his naval flight officer wings in October 1987. Currently, he is attached to Attack Squadron 42 at Naval Air Station Oceana.
^ROSS: Another Look
By p
commander Robert F. Barry, U. S. Navy
c°uld
Plex
feather oceanographic satellite that
°cean
environment is critical. However,
alC°nc* e'enlent of his professional note, e|y the assertion that N-ROSS pro-
a “new dimension” in ASW, needs
q n the September 1987 Proceedings, aPtairi David C. Honhart assessed the ential cost-effectiveness of the Navy R0s°te ®cean Sensing System (Ns , ^) oceanographic satellite, which is tiled to launch in Fall 1991. (See p '^OSS: A New ASW Dimension,” -n '!•) His case for a high-resolution,
ntap the acoustic regimes in a com- ocean environment is well pre- ed. To properly employ our antisub- toarine Warfare (ASW) assets as well as evaluate our adversaries’ tactics, a 0r°ugh and detailed knowledge of the tarn, v'des
3 Cj°Ser look, of f ^"ROSS sensor package consists i^j "Ur instruments: the low-frequency cia^r°Wave radi°meter (LFMR); the spe- alti Sensor microwave imager; a radar oteter; and the scatterometer. The C* N-ROSS sensor for providing atid Sca*e synoptic maps of ocean fronts du ,eddies is the LFMR. The LFMR is a pas *requency (5.2 and 10.4 gigahertz) lUtiIVe receiver that delivers coarse reso- 1 a (25 kilometers spatial and 1.0 to tUre |'e*vin thermal) sea surface tempera- vantUata under some conditions. Its ad- sys(a®e over already on-orbit infrared ■[yli^>n's is its ability to penetrate clouds. Point *n ^ICt’ h;ls been its major selling (for 'n Edition to its lack of resolution and CornParison, the National Oceanic (1^0a ^trnosPheric Administration’s kiloml’Sl infrared sensor delivers 1.1 qlaiITIelcrs spatial and 0.2° Kelvin ther- dr;,,,rLesoluti°n), N-ROSS has two other
^backs;
(thaa!n rate limitation—A light drizzle
the i e’tvvo millimeters per hour) negates LFMR.
► Side-lobe contamination—A predecessor of the LFMR, the 6.6 gigahertz microwave channel on SeaSat, a 1978 Oceanographic Satellite, experienced severe side lobe contamination that rendered the data useless within 600 kilometers of land.1
N-ROSS has a much larger low- frequency microwave antenna so some improvement in reducing side lobe contamination should be expected. Even with a tenfold improvement in side lobe suppression, consider this limitation in concert with the LFMR’s other drawbacks and factor out ASW areas where the LFMR would be useless. A partial list would include: the Mediterranean Sea; the Korea Strait and most of the Sea of Japan; coastal upwelling areas off the U. S. West Coast and in the North Arabian Sea; the Kuroshio Current off Japan and Okinawa; parts of the Gulf Stream;
and most of the Greenland-Iceland- United Kingdom gap.
If N-ROSS is a “new dimension,” what does the old dimension look like? Perhaps the best routine (three times a week) fronts-and-eddies analysis is done by NOAA, using conventional information and infrared sensors on the current series of NOAA polar orbiting and geostationary satellites (Figure 1). To date, no simulation has been done to show that LFMR data will actually improve on current techniques. Most pro-LFMR arguments have been simple handwavings: “If we could only see through clouds, our computers could do so much better,” rather than a systematic evaluation of projected versus current capability.
Even more important, what will the competitive oceanographic satellite environment be in N-ROSS’s projected future? Both the Japanese and Europeans
*The term “glidepath” as used here is intended to include both the glideslope and the course.
aged in a mishap. The laser beam’s divergence is range-adjusted and is wide enough to cover the entire windscreen area and eliminate any eye hazard, but not so great as to degrade atmospheric penetration or to affect the beam’s low- probability-of-intercept character.
The holographic plate is a large transparent plate cropped to fit on the pilot’s glareshield. The plate is retractable for phases of flight other than landing. It does not require any power from the aircraft, and it is even possible to have a right seat repeater plate for instructor or copilot use in aircraft such as the A-6 Intruder.
For the NCLS display, the general optical geometry is shown in Figure 5. The incoming laser beam strikes the plate from one side at a known incident angle and selected frequency. From the pilot’s eye view (on the other side of the plate), a single hologram becomes visible, consisting of several boxes apparently located out in space ahead of the aircraft. Note that the lines of the nearer boxes are slightly thicker than the boxes farther ahead, as an extra depth cue. To avoid possible alteration of the image caused by the presence of a holographic heads-up display (HHUD), when NCLS is in use, the HHUD retracts.
For each image selected for the Nickels display, a complementary image may be selected for display on the LSO’s HHUD. This image can supplement and enhance the LSO’s horizon reference, and could even include a true waveoff window. The window would be manually adjustable to suit varying recovery conditions, pilot abilities, and LSO preferences.
Another advantage is that the system is not limited to maximum amplitudes of ship motion. With NCLS, not only can the display be stabilized for any ship motion, but aircraft can be permitted to land at greater rates of deck motion than even the Manually Operated Visual Landing Aid System allows. This is because the exact range and closing speed of the aircraft are known, as well as the period of