54. BULLETIN 1136, U. 8. DEPARTMENT OF AGRICULTURE 
proper one of these 11 schedules, it has been found advantageous to 
develop special schedules for certain purposes. A number of these 
follow. 
AIRCRAFT LUMBER 
Many kiln runs and many thousands of strength tests have proved 
that the aircraft schedules of Tables 6 and 7, if carefully followed, 
will deliver stock that is just as strong in every way as the most 
carefully air-seasoned equivalent stock. ‘These schedules, prepared 
by the forest products laboratory, have been the standard for the 
Army and the Navy air services since 1917. They are intended for 
thicknesses of 3 inches or less; with heavier stock the temperature 
should be lowered 5° F. for each inch increase in thickness. 
TABLE 6.—WSpecial kiln-drying Schedule 101 for aircraft lumber* 
Dry-bulb| Wet-bulb Relative 
Moisture content at which changes should be made, per cent tempera- | tempera- 
acs are humidity 
Se th ORR Per cent 
SOTO TAT IT OT ease Se eI SS i Fey ape Bes pM i eg 120 iis 80 
ASAD iNeed Cn ae aE eR ea nig ERs eer eRe Cra EM e  efe npn Dis BNET See es Tn 125 114 70 
C7, ee Le Be scp nl veel Paes RTE Pula ebm tee ie, Cafe tn eR Ca oN de 6M ie Sil rio 128 112 60 
EUS eRe Re Dae OE oly By 2 lie Le th eye Se a BP idaeet NU LR eR SI RTA as SUD aU ote ee ACRE 13 112 44 
MUD re NES PhS ANN ase a ee a reek SNL Ne Pa Cope Sk Be Oe a ERS OE ae ope la UON 142 112 39 
Se Ne anh gS DRE a Sr 2 ES oe oh ae aS ema li a gaa NE NY Stl 145 110 33 
TTT Ea] feat Sale aS aia rapt d SIP MS Rd EY 5S PS Sy eee cn ies Ve pea eg te ts 145 110 33 
1 For use with the following species of wood: Ash, blue, white, and Biltmore white; birch, yellow; cedar 
incense, northern white, western red, and Port Orford; cypress, southern; maple, silver and sugar; pine 
sugar, northern white, and western white; spruce, red, white, and Sitka. 
TABLE 7.—Special kiln-drying Schedule 102 for aircraft tumber* 
Dry-bulb| Wet-bulb Relative 
Moisture content at which changes should be made, per cent tempera- | tempera- Hanae 
ture ture y 
Om: oR Per cent 
Pa Dio) ya 0 KGS = Yate Re Bf oY A ro es Ws DN Me pote Aa BR eB a A 105 100 84 
PAG eGR rap PAR dpe a yeste Anta tense ee GN Srermar| Sc inde et Tee gS) SRN SS ob eT A 110 101 73 
D0) EARS ah Ue esd IASI ANE Ce ai Aes EA Gh Tia, Cee are Re ad) eae EL SR 117 103 62 
SD sR eres en UN ai aN Che ancl peg Vi acc Ua ad ee Obed Yah Drag V See NU a te 129 106 46 
1 PSS eT is eg ube Re cee pm AN Sel ee NL eS NR eae UN nS at oa 135 109 43 
Lo HOU oa Re Ur ee NR ach edad Oe A DS Se HA an OR RE OS OE ae a 135 107 40 
1 Dili a2) Le agen ene Gee IL IER Ye eR Ohms bint) oe As NIE ped NN AN re ye 135 107 40 
1 For use with the following species of wood: Cherry, black; Douglas fir; mahogany; oak, red and white; 
walnut, black. 
DOUGLAS FIR 
The kiln drying of common grades of softwood lumber often 
presents problems different from those encountered in the drying 
of upper grades. One of these problems is to secure a reasonably 
uniform final moisture content; this problem is of importance when 
the average final moisture content is comparatively high, say be- 
tween 15 and 20 per cent, which is present practice in drying common 
grades of Douglas fir. Another problem is to keep the degrade 
from loose and fallen knots to a minimum. The best present solu- 
tion to these problems lies in the use of comparatively low temper- 
atures and of high humidities throughout the kiln run, and to main- 
tain these conditions satisfactorily requires a very rapid and uniform 
