Advisory US.Deportmenl of Tronspor10tion CircularFedelal Aviation Administration Su1>jec1: FLIGHT RECORDER ANO COCKPIT VOICE Dalt: 4-19-83 AC No: 21-lOA RECORDER UNDERWATER LOCATI NG DEVICES lnillattdby: ANM-110 a.a,.,
1. PURPOSE. Thi s adviso ry ci rcular prov i des an accept able means of showing compliance with the underwat er l ocat i ng device (ULO) requireme nts of the Fed&ral Aviation Regulatio ns (FAR) for recorder ULD's. Like all advisory circular mater ial , i t is not mandatory and does not constit ute a regulation. It is for guida nce purposes and to provide an exampl e of a metho d whi ch has been found acceptable.
2. CANCELLATION. Advisory Circular 21-10, Flight Recorder Underwater Locating Devices, dated May 20, 1971, is cance 11 ed.
3. RELATED FAR SECTIONS.
a. Sect i ons ?.5.1457(9)(3) and 25. 1459(d)( 3) of the FAR.
b. Sections 121.343(f) and 121.359 (c){2)( iii ) of the FAR.
4. BACKGROUNO . Federa l Aviatio n Regulations Amendments 25-25 and 121-66 established require ments for a lJLll to ass i st in l ocating fl i ght data reco rders (FOR) under water. Amendment 121-135 established a similar ULD requirement for cockp it voice recor ders (CVR). In addition, Amendment 121-135 pP.rmitted a single ULO insta ll ation, provided the FDR and t he CVR are i nstalled adjacent to each other in such a manner that t hey are unlikely to become separated during crash impact. In most cases, acoustic beacons (ringers) have been installed as the ULD.
5. ACCEPTABLE MEANS OF COMPLIANCE. An underwater acoustical beacon is accep t able for use as a recorder lllll provided:
a. Test Criteria.
(1) Environmental Tests. The beacon is subjected to the following in the order given:
(i) Condensat i on. The beacon is cold soaked at -9° +3° C. (15° +5° F.) for 6 hours, and then immediately placed in a chamber maintained at 35° +3° C. (95° +5° F. ) , and at a relative humidity of 95 +5 percent for lll hours.
This environmental cyc le is conducted 15 ti mes. Condensatio n is not to hamper proper operation, cause corrosion of vital parts, or activate the lJLO trans mitter.
(ii) Tern erat ure Stora e • The beacon is stored at a temperature of - 54° +3° C. (- 65° +5° F. for 48 hours, and then at a temperature of 71° .:_3° C. (f60° .:_5° F.) tor 48 hours .
(iii) Vibration. The beacon is exposed to continuous scan vi brat ion for l hour in each of the three ma jor mutually perpend i cular axes.
The scan is fro m 5 to 2,000 Hz, wit h a maxi llllm total excursion of 0. 020 inches and a maximum acceleration of 3g.
(iv) Pressure. The beaco n is exposed to an external pressure of 8 , 700 psi for a period of 5 minutes. The p ressure may be applied as a uniform ly di s tri buted fo rce in an incompressible liq uid as would be exerted at an ocean depth of 20,000 feet.
(v) Impact. The beacon or beacon insta ll ation package, as app li cablP., i s exposed to a half sine wave impact shock having a peak acceleration of l,OOOg. The time du ration at the base of the half sine wave should be at least 5 milliseconds. Apply the i mpact shock in the most critical di rect ion . The shoc k may 1:>e applied by placi ng the beacon or beacon installat i on package, as applicahle, on a fl at surface and acce l erating the surface.
(vi) Static Crush. The beacon is exposed to a static crush force of 5,000 pounds fo r 5 minutes. Apply the crush force in the most critical direc tion . The crush force may be applied by placi ng the beacon between two flat surfaces and bringi ng the su r faces togethe r unt il the 5,000 pound force is developed.
b. Pe rformance . The beacon utilized for the above environmental tests is exposed to the fol lowing performance tests upon completion of the environmental tests:
(1) Output freq uency: 37.5 .:_l kilohertz;
(2) Minimum pulse length: 9.0 milliseconds ;
(3) Minimum pulse repetition rate: 0.9 pulse per second;
(4) Minimum in itial acoustical output as tested in fresh water: 1,500 dynes per square centi meter peak pressure at 1 meter distance;
(5) Operating lif e: 30 days;
(6) Mi ni mum acoustical output afte r 30-day operat i on: 1, 000 dynes per squa re centimeter peak pressurP., at 1 meter di stance;
(7) Actuat i on: Wi thin 4 hours after i111t1ers ion in fresh water or salt water, at all depths to 20,000 feet;
(8) Operating temperat ure range: -2° to +3!l° C. (21l0 to +100° F. ); and
(9) Operat i ng depth range: Surface to 20,000 feet .
c. Insta llation .
(1) The Ul.0 is installed such that it is unlikely to separate from its associated FOR or CVR, or that the ULD, FDR, CVR package of single ULD installatio ns is unlikely to become separated when subjected to crash ifll)acts .
The l,OOOg impact shock test criteria specified in paragraph 5a(l)(v) have been found acceptable in demonstrating that the beacon and associated recorder or recorders are unlikely to separate when subjected to crash impacts. In lieu of the actual i mpact test, a crash condition analysis has also been found acceptable that substantiates the ULO package's ability to meet the l,OOOg ilfC)act shock test parameters specified in paragrap h 5a(l)(v).
(2) The installed ULO rad iates its rated free space acoustic output over 80 percent of a spherical pattern. If more than one beacon is necessary to achieve that pattern, the inst allat i on should include sufficient beacons in specified relative positions.
6. CERTIFICATION OF COMPLIANCE. Compliance with§§ 25. 1457(9)(3) and
25.1459(d)(6) and/or l2l.343{f} and 123.359{c ){2){ii i ) may also be achieved:
(1) th rough use of ULDs as installed by the recorder manufacturer through his compliance with all TSO and AC require ments; or (2) by installation of the ULD by the operator through use of approved manufacturer's field service bulletin and installation kit, provided mounting and clearance are adequate for those recorder installations not presently equipped with the ULO.
KEITH Manager, Aircraft Certification Division