Re: Twinjet single-engine performance question

From:         kls@ohare.Chicago.COM (Karl Swartz)
Organization: Chicago Software Works, Menlo Park, California
Date:         04 Oct 95 22:52:30 
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>I understand a twin has to be able to take off and fly on a single
>engine and therefore under normal conditions (with both engines) it
>is way overpowered.

>How overpowered are we talking?

This came up here years ago, and I went off and compiled a table of
thrust-to-weight ratios for various "typical" configurations at MGTOW.
The discussion is in the archives at http://www.chicago.com/airliners
but it's been so long it seems like it might be interesting to revisit
it.  Here's the table again, sorted by thrust/weight with all engines
operational:

model		pass	range	MGTOW	engines		thrust	p/wt	1out
-----		----	-----	-----	-------		------	----	----
Concorde	100	    ?	408	4 Olympus593	38000	0.3725	0.2794
757-200		186-220	 4550	220	2 PW2037	38250	0.3477	0.1739
737-500		108-132	 2500	115.5	2 CFM56-3B1	20000	0.3463	0.1732
MD-90-40	208	    -	163.5	2 V2500-D5	28000	0.3425	0.1713
A321-100	180-220	    ?	181.2	2 CFM56-5B2	31000	0.3422	0.1711
A320-200	140-179	    ?	162	2 CFM56-5A3	26500	0.3272	0.1636
MD-90-30	172	    -	156	2 V2500-D5	25000	0.3205	0.1603
757-200		186-220	 4550	240	2 PW2037	38250	0.3187	0.1594
737-300		141	 2950	139	2 CFM56-3B2	22000	0.3165	0.1583
737-400		159	 2800	150.5	2 CFM56-3C1	23500	0.3123	0.1561
DC-9-10		 85      1300	 90.7	2 JT8D-7	14000	0.3087	0.1544
A300-600R	230-375	    ?	375.9	2 CF6-80C2	57900	0.3081	0.1540
767-200		174-290	 4566	315	2 CF6-80A	48000	0.3048	0.1524
767-300(ER)	204-290	 6650	400	2 PW4060	60000	0.3000	0.1500
MD-11		293-410	 7980	618	3 CF6-80C2D1F	61500	0.2985	0.1990
737-300		141	 2650	135.5	2 CFM56-3B1	20000	0.2952	0.1476
767-300(ER)	204-290	 6650	400	2 CF6-80C2	57900	0.2895	0.1447
A330		280-440	    ?	467.5	2 CF6-80E1A2	67500	0.2888	0.1444
DC-10-30	250-380	 6357	572	3 CF6-50C2	52500	0.2753	0.1836
767-300		204-290	 4650	351	2 CF6-80A	48000	0.2735	0.1368
767-200(ER)	174-290	 5942	351	2 CF6-80A	48000	0.2735	0.1368
DC-10-10	250-380	 4123	440	3 CF6-6D	40000	0.2727	0.1818
MD-83		155	 2618	160	2 JT8D-219	21700	0.2712	0.1356
DC-8-71		259         ?	325	4 CFM56-2C1	22000	0.2708	0.2031
747-200B	366-452	 7570	833	4 JT9D-7R4G2	54750	0.2629	0.1972
747-400		412-509	 8380	870	4 PW4056	56000	0.2575	0.1931
DC-9-50		135      1260	121	2 JT8D-15	15500	0.2562	0.1281
727-100		 94	 2530	170	3 JT8D-9	14500	0.2559	0.1706
747-100		500	    ?	733	4 JT9D-7	45600	0.2488	0.1866
737-200(A)	120	 2840	128.6	2 JT8D-17A	16000	0.2488	0.1244
727-200(A)	145	 2240	191.5	3 JT8D-15A	15500	0.2428	0.1619
A340-300	280-440	    ?	558.9	4 CFM56-5C2	31200	0.2233	0.1675
A340-200	220-440	    ?	558.8	4 CFM56-5C2	31200	0.2233	0.1675
DC-8-61		259      5460	325	4 JT3D-3B	18000	0.2215	0.1662
DC-8-50		116-189     ?	325	4 JT3D-3B	18000	0.2215	0.1662

>And has the extent of overpoweredness been consistent over time?

Apparently not -- the 757-200 is a rocket, but the 737-200 Advanced is
quite a slug.  After Concorde, the top of the list is packet with twins
but all of them are fairly new until you get down a fair bit.  None of
the new twins are amongst those down at the bottom of the list.

--
Karl Swartz	|Home	kls@chicago.com
		|Work	kls@slac.stanford.edu
		|WWW	http://www.chicago.com/~kls/
Moderator of sci.aeronautics.airliners -- Unix/network work pays the bills