AC 21-4B

Advisory circular · Special Flight Permits for Operation of Overweight Aircraft

Approved
July 30, 1969
Last reviewed
January 20, 2017
Family
AC 21-4 · 1 version
Revision
B
14 CFR parts
21
14 CFR sections
§ 21.199§ 21.197(b)

Guidance, not mandatory unless a rule or AD requires it. DRS record last changed November 21, 2025.

AC NO: 21-4B DATE: 7/30/69

ADVISORY

CIRCULAR

DEPARTMENT OF TRANSPORTATION

FEDERAL AVIATION ADMINISTRATION SUBJECT: SPECIAL FLIGHT PERMITS FOR OPERATION OF OVERWEIGHT AIRCRAFT

1. PURPOSE. This circular provides information and guidance with respect to application for, and issuance of special flight permits to operate an aircraft in excess of its maximum certificated takeoff weight, for flight beyond the normal range over water, or over land areas where adequate landing facilities or appropriate fuel is not available.

2. CANCELLATION. AC No. 21-4At effective 9/16/66, is cancelled.

3 • REFERENCE.

a. Federal Aviation Regulations (FAR) Part 21, Sections 21.197(b) and

21.199.

b. International Flight Info~mation Manual. (This Federal Aviation Administration manual is for sale by the Superintendent of Documents,

u. s. Government Printing Office, Washington, D. C. 20402.;

4. GENERAL. FAR 21.197(b) limits the excess weight that may be authorized for overweight operations to additional fuel, fuel carrying facilities, and navigational equipment necessary for the flight. Guidance and information specifically applicable to the applicant's proposed flight may be obtained from any Federal Aviation Administration District or Area Office. The following paragraphs provide general information which should be helpful to the applicant.

a. Application for a special flight permit is made on FAA Form 8130-6 "Application for Airworthiness Certificate." (A sample form is in Appendix 1). FAR 21.199 establishes the general application requirements.

Initiated by: FS-180

Page 2 AC 21-4B 7/30/69

b. FAR Part 43 prescribes requirements for approval, return to service, and alteration records associated with the installation of additional facilities. Appendix. B of FAR Part 43 and Advisory Circular 43.9-lB give instructions for completion of the FM Form 337, on which alter­ ations are recorded.

c. lt is recommended th'at the applicant discuss the proposed flight with the manufacturer of the aircraft or an FAA-approved repair station, to determine the availability of technical data on the installation of additional fuel carrying facilities and/or navigational equipment.

d. Before flight to a foreign country of an aircraft having a special flight permit authorizing overweight operation, the applicant should determine whether operating requirements may be imposed by that country, and any other country on the route of flight, because of the condition of the aircraft. (See Section Don the reverse side of the Special Airworthiness Certificate, FAA Form 8130-7.) A request for permission to operate over or within a foreign country should include a statement describing the deviations from the FAA airworthiness standards. (Such deviations, in effect, would also be deviations from the airworthiness standards of Annex 8 to the Convention on International Civil Aviation (ICAO), since the FAA standards meet !CAO requirements.) With respect to an aircraft operating under FAR 21.197 (b), the statement may be worded as follows: 11This air~ craft does not comply with the International Airworthiness Standards of Annex 8 to the Convention on International Civil Aviation when operated at a weight in excess of its maximum certificated takeoff weight because of the addicional fuel, fuel carrying facilities, and navigation equipment installed in the aircraft. 11 (Note: The words 11and navigation equipment" should not be used if such additional equipment is not required for the flight.)

e. If the aircraft is being exported 1 the applicant must comply with any applicable requirements established by the Departments of State, Treasury. and Commerce, and, if an FAA Export Certificate of Airworthiness is required, with the applicable regulations in FAR Part 21, Subpart L. The FAA International Flight Information Manual also provides guidance with respect to the requirements for navigation and operation of aircraft in foreign countries, as well as other miscellaneous information of value to persons contemplating flights outside of the United States.

5. CRITERIA USED TO DETERMINE THE SAFETY OF ADDITIONAL FACILITIES. In approving the installation of additional facilities, the FAA DUst find that the altered aircraft is safe for operation. To assist in arriving at such a determination, the following questions are normally considered:

Par. 4

AC 21-4B Page 3 7/30/69

a. Does the technical data include installation drawings, structural substantiating reports, weight, balance, new center of gravity limits computations, and aircraft performance limitations in sufficient detail to allow a conformity inspection of the aircraft to be made?

b. In what ways does the aircraft not comply with the applicable air­ worthiness requirements (See FAR 21.199(a)(4))?

c. Are the fuel tanks vented to the outside? Are all areas in which tanks are located ventilated to reduce fire, explosion, and toxicity hazards?

d. Are the tanks even when empty strong enough to withstand the differ­ ential pressure at maximum operating altitude for a pressurized aircraft?

e. Have means been provided for determining the fuel quantity in each tank p~ior to flight?

f. Are shutoff valves, accessible to the pilot, provided for each .additional tank to disconnect these tanks from the main fuel system?

g. Are the additional fuel tank filler connections designed to prevent spillage within the aircraft during servicing?

h. Is the engine oil supply and cooling adequate for the extended weight and range?

6. LI~UTATIONS. The following types of limitations may be necessary for safe operation of the aircraft (Reference FAR 21.199(a)(6)):

a, Revised operational airspeeds for use in the overweight condition~ b, Increased pilot skill requirements.

c. A prescribed sequence for using fuel from various tanks as necessary to keep the aircraft within its center of gravity range.

d. Notification to the control tower of the overweight takeoff condition to permit use of a runway to minimize flight over congested areas.

e. Avoidance of severe turbulence. If encountered, the aircraft should be inspected for damage as soon as possible.

Par, 5

Page 4 AC 21-4B 7/30/69 £. Notification to the nearest District or Area Office located at the point of departure from the u. S. in sufficient time for that office to determine that the aircraft still conforms to the terms and conditions of the special flight permit.

,.%"- Director --:::, Flight Standards Service Par, 6

AC 21-4B 7/30/69 Example of an Application for a Special Flight Permit for Operation in Excess of Maxiwum Certificated Takeoff Weight (Face Side) Fo,m Approved Appendix 1 Page 1 Bud~e1 B..ireill ~ No. 04-ROO ~S 0~1'41 1,..., fNf 0 1 flA. ,d~~OITA!IOH fE~ f ""Al A.Vl ,\1i0N A0MIN!STRJITl0N Afr\ 10.TION FOR AIRWO~TH!:ms crnTIFICATE INST:Ht(llONS-Fn~t or r:,pt" uo noc •rn-e 1n shJd~d Ht..U, th.ex ~;;,~~c,~~:;iv~~c-Jr~1Jdi~i~~~ 1~:::tt:1~e;~1{,~d. ~~·~~h~t::i:..;~~ Fo, spe-c1.Jl tligh: r ~rm ju complece Sections 11 and VI or V[? ~• ap ;-11o bll" ~ 1 •tc:! ! iv.r· c "" ....,..,..: , i ...11u..,, 1-1.nioo s h,l,.Mf r,,,.,,) 1 ..1ai::1,1,,H ....c oh cuLc;.M,.,nON I,._ ,~ "'v. fA.,lt, cocm,10 i;' f-,- .-,.c­.l-•fl=-:Sc,[l·,.--,­.-0---+c,, --,,-N-,­CI-~-:-,,­lu--Ci.CCOC--:!1-CS--N--,.,,.--:-,--,~-,--,,--)---+:,-.7,NC:G:-C,~C:(C'."'"""'.OC:0-:'.fl"""'.CC:!C:,ie:::'.N--~C:f,O=N~---;-----------j .;

V ~ ;; 11. A•1cu.n 1s I N!W I ! U!!D I I•""()IT f',11: Pl,l(ATION ! S H~K(!!.'f MAOI FO~:, ;."-·,_-t .,,,.• ·_ ,., ,:, .:, ,.., j ,i. ! I !STANO•~D 1'.l~wc ~rn1NbS CE.IT d•J,/tf.~ ,, .,).'ir.; r"J / : ;,...:::~_..,.,,~ I lur ,~1n I I 1.C.1toa... nc l ln,,NSl'OUj ! C(.1Df• I fuuooN ~ 1 'X I s r.r::IAl A.L ;:wc:;:T t-, ;N~55 Ct !i'TiflCATE. i ( -' .... ,1_fJ_t,~ ~.. n 1/ t :/t•m j C,6 ' I I (.,A.l5 I I 2 I l• Is I 1 I 2 I l.;,

I 5 I kl ,....,. 1-t---;­:'-"­'-'-"-'G_•_r_,o_,_._.,_._.._,._._,'­'"­"°"-­'-·_~_,N_,_ I f 0:"ftu,,~N'T'AL rJ,.J" , r~ ~;, ~J:,;,,./ i) ' .' o ,., , on.:·,,. ,•tJ / ! I ii s, ( CIAL fll C,HT 'fDMJT I f 'lit(,l{I

• ' 8 I lt~"_'.:7/o;' · /;·t,;~., · 1~ , 2 I lx .1 ,.~;r'~;;:,. -, '-j.,.·# u .1, • 11 1 1----'.J.,..4 t U:""l !.U•v fYINC[ J I ~•TIOlLINO I6 I ..,,,._.,.TYUll IUIU I J I £WT(A FNl~G i 6 I

r.~~::W.tN~ !wHt,lHfl CONlltOl 10:~1•1~1°"4

j.....11:, su•vn ,._._._<_•_o _•_ 51_0_.._v1_______ -t It -1.o.CUAU a o"' """"' o, IM'1:N 0 1,-.c DA.NCH --..--+----------­ - --------------1 _X,___,_k_,_,._,_:;_o_a_,a_,_,_<•_s_s_o•_=__c_,_.,_.,_•<_•'~'°-''~'-'·_c_,._w_,_,c_"_' ­ --------t I ::O l,: v £;;•>,1G Ot fJ,0'1 I 5 • t'I OOUCTION r1IG,-li l UTING ,y,1,.11,,,,..F-Lf A '·'l'<10 ~:' •·n':'IU5 CU!";: PC A.H · ·: , .~ .: ~/ r' _,"r1.1 '! R1;: r.•.t1. I 1J;,,-r.lf; Jr1 ...i-r.i il-·11./...r.i ~r l_1>r1:11J ..11 .,_,".~l:: Jl//1 .1!-urr) 1--r-,­,-,c-,';,----,-,,--O­O-WNS• ( ,, ,:.. ,.. ,., ,,·.··:'"'" -· h .u :J ~,.; ·,:,.. ,,.,, ; IF DEALE.~. CHECK HE~E -- j ~ C A1 1i:O:An o;,u:...r:or~ J.NO MAINTfN ANCI: ~'!:CO RDS e r-Tc-.trr:. _J .:fi:: :.;:~ ... ·1 TO TAL J. ,~,u..... r k CUIS-EOJ .'tr / .r IIJtd ,:r-:,4,• ,.,.,, :Z I cc ... ~,1.... t,1 ( f wm;

3 l~Al ~ l 1 rl 0

c. cu11,1(A710t~ - I h<:rct .• ;r-r:d:, t r',J~ I .1m 1h r: 011 ner (o, h i1 .1g~r:c~ c(ihr­ 11r ~:.i.(1 JC"swbd Jbo\·-c; th~t the 1t tcr1ft i~ :~s:isrered .,.;d, the ;:C" ~r: ul A, ,.i11.::i :, .'\1!-r. m :i! ro\1,.:-11 1n acrn ~.±1 ~rc.: .,,,.,th S,c,c1,~r, ~O I o f the rcdet~I A, 1,mo n ,\er cf 1958. a'.' J .aprtioble fie-der:.il .'\ ·.·,1t iot1 R~guh· '. ;;~, :-nJ.-: h ·. , :h,: .:.: ~.. ,! r: ~~ \ ~ r n ·. :i ~rc~·,~-:..l ~-:Co! :l , :r -;,.,:,.r !~ ~· 1.~J c1:_,:: ~le "<" ~ ! !'l e .,:~·,1. )n ~•r:eH ~c-n;~ t .,tc re<-;,1e:ltc-d -----·---------- ­------- - ----------------- - ---- ­ 1 s1 c;,,,u,? v tt I .:.. r~,!: .1, li: ~ ·.r~ .:-:: ~:: ~E C~~ ~:. ·- ~ ... ... ~ 3~!:N J""IS~! C EI) ... ... o F~ l,,JO ,t, •;,·., Q ,H!-IY 61', t C<- ~/.' r:t t ,'; 11 ·, , ,, ,. ;i> Jf i-,i ,=l. :!L ." iiJ r .lJ Jp;ltn;

'"'" ~,U T 1 l i 0 1 1 27 (t i'Ttl i<,t, 1, " OLotl -· (i,.~ j I ' Ct•11f:~.1o;f !) ""((H.6.-.0C , 0 1<T I I I Cfttlfl(A f H> .,,,. ..11 il.t.llON' (G 1u (Jmp,t.,m 1 (',a,,~, ..,, , ,-, I IJ I l&r1,/•,.,.:, S , ) 6 N•) FJ~ •1Dc ~...-,r ,.,.......,.v,A.Clu,i,n rG,, t :-.J- o/ F1"" J ~-------------1 lrlTLf I_, '1·1-w::·c. ~ I Richard C. Smith

Appendix 1 AC 21-4B Page 2 7/30/69 Example of an Application for a Special Flight Permit for Operation in Excess of Maximum Certificated Takeoff lie igh t (Reverse Side) u N.&..., AOOlfU.I z~~--------------------'------------------------~~E ~:: ( ; P~ooucnC" c~~TiflC.'iiTE ,c.•:, r'°"'.:l:1,·: ,..,, ,-fr,'~':·_,!( ,,·,,:•';tr)'----------------------------1 83 J I TT' 0 £ (U!'!'l1fCJ,. TE CNL.., f~l------·'--•_P~_,._o_v_io_•_•c_o_u_a_,o_~_,~_s_•_,c_r_,o_N_sv_s_r_,M______________________ _ ~ c:. CIVE b-U>NTnv Of cumFrCAlE$ ~!·.:)t,Jlf:.tO ~c~ C?U/\TIN:(; :~u:o~ .

N ....-.if AN:) <ITLf fi'o!-11 . , : ,,'•) I A. DESOl?'r!ON OF A:~('1:Afl Iitt~IS,e.:.:0 ow,,.u j •OOilUS 1492 ~orth Street ~hn J. Doe r St. Louis, Missouri 12345 il:JILC.tl f ',L.JU) IMCCEL i 6eec_h_________________ _! ____D""S"-_Oc;A_._________ Iro _ 0H,,o.,n,.,o.cl.:u.._._lu,._,_,_.,H.,,a"'w"a._,i,,.1._· ,-•. ,·.-,­.

1 o{,...i,.;•E o...r1 l 0 .. ...,....

________ ---1 !5tll..,L1'oUMIU 1 41'1 ,. ~t 5.( .,;;•riO!'i or FuGt1 r ... t------ ­ ~ j~tOM . .

x I St . Lo__ll_~ , )11 s so,g:_i ~-~---------;

2 z Oakland, California 1_ July 15. 1969 I 15 daH ; !:::::::::::::~:~:'!'!:-~:,~:,~:~:~c!},::~~~·:::E:~:cc;[,·~~,, ,s ,a,tows~.. ::__c=:c-:..=------------------1The air_cx-aft does not meet the applicable ain.oX'thiness x-equirements "'hen operated at a weight in excess of its certificated weight of 6300 lbs. The temporary fuel tank installation is in accorda~ce wich Flight Inc., Dra...,ing 2-26189 and FAA Form 337 "l'!ajor Repair and Alt.eration" dated June 15, 1969, issued by CE-GAD0-17.

. ~---------------------~ ~ ~ T·~: ~CllCN·"~ -=:tSPJ(TIC"'•~ t.~'.; .'.:·..:~,~ ;;:~:::, :,f :~! ~--~' ~:1 ~~:e O~!'-~AilON , ( -,,, _,_,_._.•; ••·,.,.: ;;· nll•.".J_n_J_________ ---< 0: ~ti'en the aircraft is ov·~-r~;-i0t :-ch~~--;:-~isin~ speed (Ve) should not exceed ~ 185 ,n.p.h. ar.d the :aaxiinuai speed ('·.'ne) should not exceed 205 m.p.h.

;' The sequence:: oi use tor cht .auxiliar:: fi;E:l tanks, as shown by a teltlporary placard o:i the i~scru:::ie;it ;:a~.c-i, shol;lG be aft, forward, center.

3. The fuel Gua~ticy should ~Jt txc~ed 106 gallons in the forward ta~k, !64 gallons in the center t2nk, and 45 gallons in the aft tank.

>

Appendix 1AC 21-4B Page 37/30/69 Example of a Special Airworthiness Certificate Issued to Permit Operation in Excess of Maximum Certificated Takeoff Weight

UNITED STATES OF AMERICA

DEPARTMENT OF TRANSPORTATION - FEDERAL AVIATION ADMINISTRATION SPECIAL Al RWOR'T]i1N.ESS CERTIFICATE CLASS I Fl CATION: Special Fligl1 t Per~itA -~ . PURPOSE: Operation in ~:,Q:~Ys of max.., certificated T.O. weight NAME $¥A /MANLJ. -B FACTU R ER ADDRESS i...:,J./A ·­ FROM St >Louis 1 MissouriFLIGHTC TO uonolulu Ha'l:il'a ii ...N-l 234Z S.fRl!'lt- NO. 4321 ----·· --····· --+--~-----..D BU 1 LDER Beech M O,PEL D50 A DA.TE OF ,SSLANCE 7/1£[/69 E;«'tl<J 7/30/69 OPERAilNG li~ITAT ONS :CATEO:' ,7~10/69 AR& A PART OF THIS GRTIF'CATE E 01!'.SIGNATION OR OFFICE NOSIGN~FAA R!!:.R'J..ENT#>:JV£ ; C • •' /, ~ 1 . ~~. .., Richard C. Smith · · CR-1:t.nn-17 Any alterat1cm, repn:>ch•,ct~on, or m 1su,e of thi'S C(>rttficau~ m3y be pum,,.hable by il fine not exC~@ding Sl.000 or impci1onment not exceeding 3 year,, or both. THIS CERTIFICATE MUST BE DISPLAYED IN THE AIR­

CRAFT IN ACCORDANCE WITH APPLICABLE FEDERAL AVIATION REGULATIONS FAA FORM 8130-? 13-691 5UPERSE:DE:S F"AA. FOR._,.S i,3'5;,;:+0: t3IOC-::! e13c,.~ SEE REVERSE SIDE (Face Side) i This airworthiness certificate is issued u~der the authority of the Federal Aviation Act of A 1958 and the Federal Aviation Regulations \FAR).

This airworthiness certificate authorizes the manufacturer named on the reverse side to conduct production flight tests, and only production flight teots, of aircraft registered in hi• name. No person may conduct production !light tests under this certificate: ( 1) Carrying persons or property for compensation or hire: and or ( 2) Carrying persons not essential to the purpose of the flight.

B This airworthiness certificate authorizes the flight !pecified on the reverse side for the pur-C p~e shown in Block A.

This 11irworthiness certificate certifies that, as of the date of issuance, the aircraft to which issued has been inspected and found to meet the requirements of the applicable FAR. The aircraft does not meet the requirements of the applicable comprehensive and detailed air­ worthiness code as provided by Annex 8 to the Convention On International Civil Avia­ tion. No penon may operate the aircraft described on the reverse sidf': ( 1) except in accord­ ance with the applicable FAR and in accordance with conditions and iimitations which may be prescribed by the Administrator as part of this certificate; ( 2) over any foreign country without the special permission of that country.

D Unless sooner surrendered, su,pended, or revoked, this airworthiness certificate is effective for the duration and under the conditions prescribed in FAR Part 21, Section 21.lBl or

21.217.

E (Reverse Side)

Page 8 · 4Open in PDF

Appendix 1 AC 21-4B 7/30/69 Example of Operating Limitations Which May be Prescribed as Part of the Special Airworthiness Certificate Shown on Page 3 of this Appendix Aircraft Make: Beech Model: D50A Serial No: 4321 Ident. Marks: Nl234Z Issue Date: 7/10/69

OPERATING LIMITATIONS 1, Maximum weight must not exceed 8 1 150 pounds.

2. Maximum quantity of fuel carried in auxiliary tanks must not exceed 106 gallons in fwd tank, 164 gallons in center tank, and 45 gallons in aft tank.

3. Center of gravity limits must not exceed (fwd) +116.8 and (aft) +124 .6.

4. Acrobatics are prohibited,

5. Use of autopilot while in overweight condition is prohibited, 6, Weather conditions with moderate to severe turbulence should be avoided.

7, When an overweight landing is made or the aircraft has been flown through 1DOderate or severe turbulence while in an overweight con• dition, the aircraft must be ins~ected for damage after landing, The inspections performed and the findings must be entered in the aircraft log. The pilot must determine, before the next ta1':eoff 1 that the aircraft is airworthy.

8. When operated in the overweight condition, the cruising speed {Ve} shall not exceed 185 m.p.h. and the maximum speed (V11e) shall not exceed 205 m.p.h.

9. Operation in the overweight condition must be conducted to avoid areas having heavy air traffic, to avoid cities, towns, villages, and congested areas, or any other areas where such flights might create hazardous exposure to person or property on the ground.

10. Prior to requesting clearance to takeoff position 1 the pilot in command must advise the tower of the overweight condition and of any limitations with respect to a specific runway or prescribed meteorological conditions.

11. 1he pilot-in-command shall contact the Oakland General Aviation District Office (WE-GAD0-7), 9636 Earhart Road, P. 0, Box 2397, Airport Station, Oakland, California 94614, telephone (415) 569-8879, prior to arrival at Oakland, in sufficient time for review of the ferry permit and FM inspection of the aircraft before departure for Honolulu,