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Airspeed Sensor Switch

 
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Troy Maynor



Joined: 10 Jan 2006
Posts: 162
PostPosted: Mon Mar 10, 2008 7:44 am    Post subject: Airspeed Sensor Switch Reply with quote
Hi All,
Does anyone have an idea what 60 knots equates to in PSI? I'm trying to buy an air switch that closes below a certain airspeed that is adjustable for different air speeds. I read about one on the Aeroelectric list but it apparently is for driving another electronic circuit. I want to just turn off a 12 volt circuit above a given airspeed for a gear warning system.
Thanks.
Troy Maynor
Visit - www.EuropaOwners.org

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kheindl(at)msn.com
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PostPosted: Mon Mar 10, 2008 8:34 am    Post subject: Airspeed Sensor Switch Reply with quote
I have a Hobbs meter connected to an adjustable low pressure switch for recording actual flight time.
It happens to be the same switch as the one used by the Europa stall warner kit, also supplied by RS Components. I can dig up the order number if you are interested.

Karl



<html><div></div></html>

Quote:
Subject: Airspeed Sensor Switch
From: wingnut54(at)charter.net
Date: Mon, 10 Mar 2008 17:41:32 +0200
To: europa-list(at)matronics.com

--> Europa-List message posted by: "europaman" <wingnut54(at)charter.net>

Hi All,
Does anyone have an idea what 60 knots equates to in PSI? I'm trying to buy an air switch that closes below a certain airspeed that is adjustable for different air speeds. I read about one on the Aeroelectric list but it apparently is for driving another electronic circuit. I want to just turn off a 12 volt circuit above a given airspeed for a gear warning system.
Thanks.
Troy Maynor






Visit - www.EuropaOwners.org




&====================

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jan.de.jong(at)xs4all.nl
Guest
PostPosted: Mon Mar 10, 2008 10:18 am    Post subject: Airspeed Sensor Switch Reply with quote
I have a program output with calculated airspeed in mm/s (column 3) vs
pitot-static pressure in Pa (column 2). I hope I'm attaching it.
You can find "pressure conversion" to psi or "H2O and "velocity
conversion" using Google.
Hope this is of use.
Regards,
Jan de Jong

europaman wrote:
Quote:


Hi All,
Does anyone have an idea what 60 knots equates to in PSI? I'm trying to buy an air switch that closes below a certain airspeed that is adjustable for different air speeds. I read about one on the Aeroelectric list but it apparently is for driving another electronic circuit. I want to just turn off a 12 volt circuit above a given airspeed for a gear warning system.
Thanks.
Troy Maynor


indicated airspeed, middle regime
omit every second from lookup table (gives max. deltas as shown)
d-pressure ind-airspeed interpolated delta d_prev max-res
Pa mm/s mm/s mm/s mm/s mm/s
0 512 28886 28829 -57 1862 29
576 30635 30587 -48 1749 27
1 640 32289 32248 -41 1654 25
704 33861 33825 -36 1572 24
2 768 35362 35331 -31 1501 23
832 36802 36774 -28 1440 22
3 896 38187 38162 -25 1385 21
960 39523 39501 -22 1336 20
4 1024 40815 40794 -21 1292 20
1088 42066 42048 -18 1251 19
5 1152 43281 43264 -17 1215 18
1216 44462 44446 -16 1181 18
6 1280 45612 45597 -15 1150 17
1344 46733 46719 -14 1121 17
7 1408 47827 47815 -12 1094 17
1472 48897 48885 -12 1070 16
8 1536 49943 49932 -11 1046 16
1600 50967 50957 -10 1024 16
9 1664 51971 51961 -10 1004 15
1728 52955 52945 -10 984 15
10 1792 53920 53912 -8 965 15
1856 54869 54860 -9 949 14
11 1920 55801 55793 -8 932 14
1984 56717 56709 -8 916 14
12 2048 57618 57611 -7 901 14
2112 58505 58498 -7 887 13
13 2176 59378 59371 -7 873 13
2240 60238 60232 -6 860 13
14 2304 61086 61080 -6 848 13
2368 61922 61916 -6 836 13
15 2432 62746 62740 -6 824 12
2496 63559 63554 -5 813 12
16 2560 64362 64356 -6 803 12
2624 65154 65149 -5 792 12
17 2688 65936 65931 -5 782 12
2752 66709 66704 -5 773 12
18 2816 67473 67468 -5 764 11
2880 68228 68223 -5 755 11
19 2944 68974 68970 -4 746 11
3008 69712 69708 -4 738 11
20 3072 70442 70438 -4 730 11
3136 71164 71160 -4 722 11
21 3200 71879 71875 -4 715 11
3264 72586 72582 -4 707 11
22 3328 73286 73283 -3 700 10
3392 73980 73976 -4 694 10
23 3456 74666 74663 -3 686 10
3520 75346 75343 -3 680 10
24 3584 76020 76016 -4 674 10
3648 76687 76684 -3 667 10
25 3712 77348 77345 -3 661 10
3776 78004 78000 -4 656 10
26 3840 78653 78650 -3 649 10
3904 79297 79294 -3 644 10
27 3968 79936 79933 -3 639 9
4032 80569 80566 -3 633 9
28 4096 81197 81194 -3 628 9
4160 81820 81817 -3 623 9
29 4224 82438 82435 -3 618 9
4288 83051 83048 -3 613 9
30 4352 83659 83657 -2 608 9
4416 84263 84260 -3 604 9
31 4480 84862 84860 -2 599 9
4544 85457 85454 -3 595 9
32 4608 86047 86045 -2 590 9
4672 86633 86631 -2 586 9
33 4736 87215 87213 -2 582 9
4800 87793 87791 -2 578 9
34 4864 88367 88365 -2 574 8
4928 88937 88935 -2 570 8
35 4992 89503 89501 -2 566 8
5056 90065 90063 -2 562 8
36 5120 90623 90621 -2 558 8
5184 91178 91176 -2 555 8
37 5248 91729 91727 -2 551 8
5312 92277 92275 -2 548 8
38 5376 92821 92819 -2 544 8
5440 93362 93360 -2 541 8
39 5504 93899 93897 -2 537 8
5568 94433 94431 -2 534 8
40 5632 94964 94962 -2 531 8
5696 95492 95490 -2 528 8
41 5760 96016 96015 -1 524 8
5824 96538 96536 -2 522 8
42 5888 97056 97055 -1 518 8
5952 97572 97570 -2 516 8
43 6016 98084 98083 -1 512 8
6080 98594 98592 -2 510 7
44 6144 99101 99099 -2 507 7
6208 99605 99603 -2 504 7
45 6272 100106 100105 -1 501 7
6336 100605 100603 -2 499 7
46 6400 101101 101099 -2 496 7
6464 101594 101593 -1 493 7
47 6528 102085 102083 -2 491 7
6592 102573 102572 -1 488 7
48 6656 103059 103057 -2 486 7
6720 103542 103541 -1 483 7
49 6784 104023 104021 -2 481 7
6848 104501 104500 -1 478 7
50 6912 104977 104976 -1 476 7
6976 105451 105449 -2 474 7
51 7040 105922 105921 -1 471 7
7104 106391 106390 -1 469 7
52 7168 106858 106856 -2 467 7
7232 107322 107321 -1 464 7
53 7296 107785 107783 -2 463 7
7360 108245 108244 -1 460 7
54 7424 108703 108702 -1 458 7
7488 109159 109157 -2 456 7
55 7552 109612 109611 -1 453 7
7616 110064 110063 -1 452 7
56 7680 110514 110513 -1 450 7
7744 110962 110960 -2 448 7
57 7808 111407 111406 -1 445 6
7872 111851 111850 -1 444 6
58 7936 112293 112292 -1 442 6
8000 112733 112732 -1 440 6
59 8064 113171 113170 -1 438 6
8128 113607 113606 -1 436 6
60 8192 114041 114040 -1 434 6
8256 114474 114472 -2 433 6
61 8320 114904 114903 -1 430 6
8384 115333 115332 -1 429 6
62 8448 115760 115759 -1 427 6
8512 116186 116184 -2 426 6
63 8576 116609 116608 -1 423 6
8640 117031 117030 -1 422 6
64 8704 117452 117450 -2 421 6
8768 117870 117869 -1 418 6
65 8832 118287 118286 -1 417 6
8896 118702 118701 -1 415 6
66 8960 119116 119115 -1 414 6
9024 119528 119527 -1 412 6
67 9088 119938 119937 -1 410 6
9152 120347 120346 -1 409 6
68 9216 120755 120753 -2 408 6
9280 121160 121160 0 405 6
69 9344 121565 121564 -1 405 6
9408 121968 121967 -1 403 6
70 9472 122369 122368 -1 401 6
9536 122769 122768 -1 400 6
71 9600 123167 123166 -1 398 6
9664 123564 123563 -1 397 6
72 9728 123959 123958 -1 395 6
9792 124353 124352 -1 394 6
73 9856 124746 124745 -1 393 6
9920 125137 125136 -1 391 6
74 9984 125527 125526 -1 390 6
10048 125916 125915 -1 389 6
75 10112 126303 126302 -1 387 6
10176 126689 126688 -1 386 6
76 10240 127073 127072 -1 384 6
10304 127456 127455 -1 383 5
77 10368 127838 127837 -1 382 5
10432 128219 128218 -1 381 5
78 10496 128598 128597 -1 379 5
10560 128976 128975 -1 378 5
79 10624 129353 129352 -1 377 5
10688 129728 129727 -1 375 5
80 10752 130102 130102 0 374 5
10816 130476 130474 -2 374 5
81 10880 130847 130847 0 371 5
10944 131218 131217 -1 371 5
82 11008 131587 131587 0 369 5
11072 131956 131955 -1 369 5
83 11136 132323 132322 -1 367 5
11200 132689 132688 -1 366 5
84 11264 133053 133053 0 364 5
11328 133417 133416 -1 364 5
85 11392 133779 133779 0 362 5
11456 134141 134140 -1 362 5
86 11520 134501 134500 -1 360 5
11584 134860 134859 -1 359 5
87 11648 135218 135217 -1 358 5
11712 135575 135574 -1 357 5
88 11776 135931 135930 -1 356 5
11840 136286 136285 -1 355 5
89 11904 136640 136639 -1 354 5
11968 136992 136992 0 352 5
90 12032 137344 137343 -1 352 5
12096 137694 137694 0 350 5
91 12160 138044 138043 -1 350 5
12224 138392 138392 0 348 5
92 12288 138740 138739 -1 348 5
12352 139086 139086 0 346 5
93 12416 139432 139431 -1 346 5
12480 139776 139776 0 344 5
94 12544 140120 140119 -1 344 5
12608 140463 140462 -1 343 5
95 12672 140804 140804 0 341 5
12736 141145 141144 -1 341 5
96 12800 141484 141484 0 339 5
12864 141823 141822 -1 339 5
97 12928 142161 142160 -1 338 5
12992 142498 142497 -1 337 5
98 13056 142834 142833 -1 336 5
13120 143169 143168 -1 335 5
99 13184 143503 143502 -1 334 5
13248 143836 143835 -1 333 5
100 13312 144168 144167 -1 332 5
13376 144499 144499 0 331 5
101 13440 144830 144829 -1 331 5
13504 145159 145159 0 329 5
102 13568 145488 145487 -1 329 5
13632 145816 145815 -1 328 5
103 13696 146143 146142 -1 327 5
13760 146469 146468 -1 326 5
104 13824 146794 146794 0 325 5
13888 147119 147118 -1 325 5
105 13952 147442 147442 0 323 5
14016 147765 147764 -1 323 5
106 14080 148087 148086 -1 322 5
14144 148408 148407 -1 321 5
107 14208 148728 148728 0 320 5
14272 149048 149047 -1 320 5
108 14336 149366 149366 0 318 4
14400 149684 149683 -1 318 4
109 14464 150001 150000 -1 317 4
14528 150317 150317 0 316 4
110 14592 150633 150632 -1 316 4
14656 150948 150947 -1 315 4
111 14720 151261 151261 0 313 4
14784 151575 151574 -1 314 4
112 14848 151887 151887 0 312 4
14912 152199 152198 -1 312 4
113 14976 152509 152509 0 310 4
15040 152819 152819 0 310 4
114 15104 153129 153128 -1 310 4
15168 153437 153437 0 308 4
115 15232 153745 153744 -1 308 4
15296 154052 154052 0 307 4
116 15360 154359 154358 -1 307 4
15424 154664 154664 0 305 4
117 15488 154969 154968 -1 305 4
15552 155273 155273 0 304 4
118 15616 155577 155576 -1 304 4
15680 155880 155879 -1 303 4
119 15744 156182 156181 -1 302 4
15808 156483 156483 0 301 4
120 15872 156784 156783 -1 301 4
15936 157084 157083 -1 300 4
121 16000 157383 157383 0 299 4
16064 157682 157681 -1 299 4
122 16128 157980 157979 -1 298 4
16192 158277 158276 -1 297 4
123 16256 158573 158573 0 296 4
16320 158869 158869 0 296 4
124 16384 159165 159164 -1 296 4

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willie.harrison(at)tinyon
Guest
PostPosted: Mon Mar 10, 2008 11:06 am    Post subject: Airspeed Sensor Switch Reply with quote
Hi Troy
My calc gives just under 0.1psi as the difference between static and pitot pressure at 60kts. I think its right but don't bet your life on it until you've got a second opinion.

Willie Harrison
G-BZNY (grounded for complete rewire and panel refit and a few other upgrades)
On 10 Mar 2008, at 16:31, Karl Heindl wrote:
Quote:
 
I have a Hobbs meter connected to an adjustable low pressure switch for recording actual flight time.
It happens to be the same switch as the one used by the Europa stall warner kit, also supplied by RS Components. I can dig up the order number if you are interested.
 
Karl
 
<html><div></div></html>

Quote:
Subject: Airspeed Sensor Switch
From: wingnut54(at)charter.net (wingnut54(at)charter.net)
Date: Mon, 10 Mar 2008 17:41:32 +0200
To: europa-list(at)matronics.com (europa-list(at)matronics.com)
 
--> Europa-List message posted by: "europaman" <wingnut54(at)charter.net (wingnut54(at)charter.net)>
 
Hi All,
Does anyone have an idea what 60 knots equates to in PSI? I'm trying to buy an air switch that closes below a certain airspeed that is adjustable for different air speeds. I read about one on the Aeroelectric list but it apparently is for driving another electronic circuit. I want to just turn off a 12 volt circuit above a given airspeed for a gear warning system. 
Thanks. 
Troy Maynor
 
 
 
 
 
 
Visit - www.EuropaOwners.org
 
 
 
 
&====================

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hdwysong(at)gmail.com
Guest
PostPosted: Tue Mar 11, 2008 1:16 am    Post subject: Airspeed Sensor Switch Reply with quote
Quote:
Hi All,
Does anyone have an idea what 60 knots equates to in PSI?

Hello Troy,

The math says the differential pressure (Pd, Ptotal - Pstatic) is
equal to 0.5*airDensity*V*V for a given velocity, V.

60 knots is roughly 100 ft/sec. Assuming a standard sea level density
and slogging through the ugly units conversions, the Pd would be ~2.65
PSI.

Pd = 0.5 * 0.002377 slug/ft^3 * 32.2 lbf s^2/ft / slug * 100 ft/s *
100 ft/s / 144 in^2/ft^2 (... told you it was ugly)

I hope that doesn't add more mud to the water.

D

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hdwysong(at)gmail.com
Guest
PostPosted: Tue Mar 11, 2008 8:08 pm    Post subject: Airspeed Sensor Switch Reply with quote
My bad, Troy...

The correct Pd is exactly what I said it was... provided you divide
the answer by the 32.2 that I inadvertently used. Our good man Willy
understands slugs (his 'uk' email domain gives him away) and steered
you in the right direction. The Pd at 60 knots is just shy of 0.1 psi
(0.08 or so).

Sorry for the bum steer. I should have worked it in SI units to
double check... Wink

D

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willie.harrison(at)tinyon
Guest
PostPosted: Wed Mar 12, 2008 12:21 am    Post subject: Airspeed Sensor Switch Reply with quote
SI, indeed, although I do the car tyres in psi. My school physics
teacher told us not to sneer at those using "imperial units" as the
Americans had got to the moon in feet and inches.

Meanwhile, my co-worker on my re-wire/panel refit job (who is 10
years younger than I am) can only think and work in inches and I have
to use mm. We have a running mutual piss take. (What's a thirty
second? Isn't that half a minute? etc)

Regarding the 60 kts question, the 0.1 psi answer passes a sabity
check if you think about the drag on your hand if you stuck it out of
a car window at 70mph: about 25 sq. in. and o.1psi and a Cd of about
1.0 giving about 2.5lb which seems broadly right. 2psi would have
given 50lbs which would couldn't be right.

Cheers

Willie H

On 12 Mar 2008, at 03:56, D Wysong wrote:

Quote:


My bad, Troy...

The correct Pd is exactly what I said it was... provided you divide
the answer by the 32.2 that I inadvertently used. Our good man Willy
understands slugs (his 'uk' email domain gives him away) and steered
you in the right direction. The Pd at 60 knots is just shy of 0.1 psi
(0.08 or so).

Sorry for the bum steer. I should have worked it in SI units to
double check... Wink

D




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david.steade(at)btinterne
Guest
PostPosted: Wed Mar 12, 2008 9:45 am    Post subject: Airspeed Sensor Switch Reply with quote
Hi

Check out this site.
http://www.iflyez.com/manometer.shtml


Regards

David Steade

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