Technical Evaluation Engineering Aerodrome Safety, Civil Aviation - TP 13706

 

Order TP 13706E

January 1998

Copyright

© Her Majesty the Queen in Right of Canada, as represented by the Minister of Transport (1998)

All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without prior written permission of the Department of Transport, Canada.

The information in this publication is to be considered solely as a guide and should not be quoted as or considered to be a legal authority. It may become obsolete in whole or in part at any time without notice.

TP 13706E
(01/1998)

TC-1001804

Table of contents

Introduction

Pursuant to a request from Transport Canada – Civil Aviation, a frost study was conducted on a number of designs of Precision Approach Path Indicator (PAPI) light units. The objective for the project is to eliminate the possibility of a false signal being presented to aircraft from a frosted PAPI, and thus to prevent a potential hazard. For more details, see terms of reference (Appendix "A").

The project is separated in 4 parts:

  1. Determine the amount of operating time required to eliminate frost 1/16" (1.6 mm) from the PAPI lens or cover glass at different temperatures (-5, -10, -20, -30°C).
  2. Determine the minimum current level for the PAPI lights to function with a partial frost accumulation on the lenses or cover glass at the same temperatures as in 1.
  3. Determine the minimum current level for the PAPI lights to function without frost accumulation on the lenses or cover glass at the same temperatures as in 1.
  4. Determine what is the effect of dew on PAPI signal at 0°C.

Test Procedure

Laboratory book for Precision Approach Path Indicator (PAPI)

Name of PAPI:

Test type:

Test Amp.:

Test number:

Test temperature:

Date:

Time:

By (initials):

Before the test:

  1. We ensured that the test equipment conformed to standards (Check for ISO stamp).
  2. We obtained the materials required to conduct the test procedures as stipulated in Canada Motor Vehicle Safety Standard, (CMVSS) 103. (paint gun, pressure regulator, Hydra, timer Cra-Lab, video camera, digital camera).
  3. We installed a white 8' x 8' panel to receive the projected signal from the PAPI'S.
  4. We installed the PAPI units on a table at the other end of the chamber (the PAPI projected the signal onto the panel surface). The supply current for the PAPI light unit was set at 6.6 Amp.
  5. We adjusted the distance of the table so that the emitted light beam just covered the width of the target panel.
  6. We lowered the temperature of the cold chamber to test temperature and confirmed this using a thermocouple measuring device.
  7. A sign identifying the test being performed was prepared.

Defrosting:

Note: For this test, it was necessary to measure the thickness of the applied frost when sprayed with water. The adopted technique was to install a measured metallic disc between the two PAPI lenses, to create frost by spraying water vapor from a paint gun equally onto the entire front surface of the PAPI unit under test, including the metallic disc. After completing the application of water, the disc was removed and the total thickness of the disc plus frost was measured using a dial caliper. The thickness of the frost was measured as the difference between the total thickness and the thickness of the metallic disc.

  1. A pre-test photograph was taken of the equipment under test.
  2. A means to measure the thickness of the frost applied on the PAPI surface was installed (metallic disc between the lenses).
  3. Vaporized water was sprayed onto the front of the PAPI unit (entire surface of optical window) to form a 1/16" thickness of frost (0.175 ml/cm2)
  4. The application of vaporized water was video-taped and a still picture was taken after the application.
  5. The metal measuring disc was removed and the total thickness of the disc plus the frost deposit was measured.
  6. The thickness of the frost was calculated.
  7. A 30 minutes time period was allowed to elapse to allow, for temperature stabilization as specified in CMVSS 103.
  8. The video camera was started, the PAPI was turned on and operated at 6.6 Amperes while simultaneously starting a timer.
  9. The end of the test was acknowledged as the moment when the signal displayed on the screen was identical to the signal displayed when the PAPI light unit was operating without any frost cover.
  10. The time required for the PAPI defrosting to the point of producing a signal the same as a PAPI without frost cover was noted.
  11. A post-test still photograph was taken.

Minimal current test:

  1. A thermocouple was attached to the centre of one of the two PAPI lenses or at the beam centre point for PAPI equipped with a cover glass.
  2. A pre-test still photograph was taken of the equipment under test and the test identification sign.
  3. The PAPI light unit was operated at the specified current test level.
  4. The test was delayed until there was a stabilization of the lens or cover glass temperature (approximately 1 hour).
  5. The lens temperature was recorded.
  6. An attempt was made to apply a thin coat of vaporized water onto the lens surface or onto the portion of the cover glass without the thermocouple. This procedure was video-taped.
  7. A verification was made to see if the frost melted immediately from the lens or cover glass.
  8. The test was considered successful if the frost melted and was eliminated. If this did not occur and permanent frost remained, the test was repeated by raising the current to the next required level.
  9. A post-test still photograph was taken with the test identification sign.

Dew test:

  1. The temperature of the cold chamber was lowered to 0 degrees Celsius. A panel was installed.
  2. The PAPI units were installed at 12' of the surface measuring the light intensity.
  3. A supplied current of one PAPI was set up at 6.6 Amp.
  4. It was left in soak for 1 hour.
  5. A photograph of the intact signal was taken.
  6. With a kettle, vapor was generated under the glass/lens to form dew.
  7. The brightness of the signal and the width of the bundle were compared and quantified approximately.
  8. The test was video-taped.
  9. A photograph of the signal with dew was taken.

Test report study of PAPI Frost/Dew

Test Period: January, 1998

Equiptment: Precision Approach Path Indicator (PAPI)

Project No. 98-5115

Test results

Dew test at 0°C

Test # PAPI Manufacturer Cover glass (Yes/No) Signal reduction RMS Current (Amp) Comments
14 Siemens No 100% 6.6 Amp Color mismatch/no signal
15 Siemens Yes/Wired 50% 6.6 Amp N/A
16 Siemens Yes/Antifog 30% 6.6 Amp N/A
17 Siemens Yes/Regular 100% 6.6 Amp No Signal
18 Cegelec N/A 20% 6.6 Amp N/A
19 Crouse-Hinds N/A 0% 6.6 Amp Dew Evaporate

Defrosting time test at -5°C *

Test # PAPI Manufacturer Cover glass (Yes/No) Ice Thickness (inch) RMS Current (Amp) Defrosting time (min.)
1 Cegelec No .060 6.6 24 minutes
2 ADB/Siemens No .060 6.6 22 minutes
3 Crouse-Hinds No .055 6.6 6 minutes
4 ADB/Siemens Yes/Wired .053 6.6 32 minutes
5 ADB/Siemens Yes/Antifog .060 6.6 32 minutes
6 ADB/Siemens Yes/Regular .060 6.6 32 minutes

Notes: * Application of water did ice instead of frost.

Defrosting time test at -10°C

Test # PAPI Manufacturer Cover glass (Yes/No) Ice Thickness (inch) RMS Current (Amp) Defrosting time (min.)
28 Cegelec No .060 6.6 30 minutes
29 ADB/Siemens No .053 6.6 26 minutes
30 Crouse-Hinds No .059 6.6 9 minutes 30 sec.
31 ADB/Siemens Yes/Wired .058 6.6 9 minutes
32 ADB/Siemens Yes/Antifog .056 6.6 18 minutes
33 ADB/Siemens Yes/Regular .065 6.6 17 minutes

Defrosting time test at -20°C

Test # PAPI Manufacturer Cover glass (Yes/No) Ice Thickness (inch) RMS Current (Amp) Defrosting time (min.)
94 ADB/Siemens Yes/Regular .070 6.6 8 minutes
95 ADB/Siemens Yes/Wired .080 6.6 5 minutes
96 ADB/Siemens Yes/Antifog .075 6.6 7 minutes
97 ADB/Siemens No/Glass .065 6.6 14 minutes
98 Cegelec No .060 6.6 19 minutes
99 Crouse-Hind No .065 6.6 6.5 minutes

Defrosting time test at -30°C

Test # PAPI Manufacturer Cover glass (Yes/No) Ice Thickness (inch) RMS Current (Amp) Defrosting time (min.)
56 ADB/Siemens No .070 6.6 30 minutes/uneven icing
57 Cegelec No .070 6.6 53.5 minutes
58 Crouse-Hinds No .065 6.6 15 min./light icing at the top
59 ADB/Siemens Yes/Regular .066 6.6 10 min/10 sec. (donut)
60 ADB/Siemens Yes/Wired .068 6.6 8 min/40 sec. (donut)
61 ADB/Siemens Yes/Antifog .070 6.6 9 min/35 sec.

Minimum current test at -5°C

Test # PAPI Manufacturer Cover glass (Yes/No) RMS Current (Amp) Lens/glass Temperature (°C) Accumulation of frost (Yes/No)
7 ADB/Siemens Yes/Regular 2.8 6.3 Yes
8 ADB/Siemens Yes/Regular 3.4 16.3 Yes
9 ADB/Siemens Yes/Regular 4.1 31.1 No
10 ADB/Siemens Yes/Antifog 2.8 6.6 Yes
11 ADB/Siemens Yes/Antifog 3.4 18.3 No
12 ADB/Siemens Yes/Wired 2.8 7.3 Yes
13 ADB/Siemens Yes/Wired 3.4 17.7 No
20 ADB/Siemens No glass 3.4 6.4 Yes
21 ADB/Siemens No glass 4.1 17.1 Yes
22 ADB/Siemens No glass 5.2 38.9 No
23 Crouse-Hinds No glass 2.8 1.4 Yes
24 Cegelec No glass 2.8 3.6 Yes
25 Cegelec No glass 3.4 11.4 Yes
26 Crouse-Hinds No glass 3.4 6.4 No
27 Cegelec No glass 4.1 22.5 No

Minimum current test at -10°C

Test # PAPI Manufacturer Cover glass (Yes/No) RMS Current (Amp) Lens/glass Temperature (°C) Accumulation of frost (Yes/No)
34 Cegelec No 4.1 19.6 Yes
35 ADB/Siemens Yes/Regular 4.1 21.3 Yes
36 ADB/Siemens Yes/Regular 5.2 47.8 Yes
37 ADB/Siemens Yes/Regular 6.6 94.5 No
38 ADB/Siemens Yes/Antifog 4.1 28.5 Yes
39 ADB/Siemens Yes/Antifog 5.2 61.3 Yes
40 ADB/Siemens Yes/Antifog 6.6 116.9 No
41 ADB/Siemens Yes/Wired 4.1 23.6 Yes
42 ADB/Siemens Yes/Wired 4.8 44.4 Yes (donut)
43 ADB/Siemens Yes/Wired 5.2 56.4 Yes small donut
44 ADB/Siemens Yes/Wired 5.5 66.3 Yes light frost
45 ADB/Siemens Yes/Wired 6.6 102.3 No
46 ADB/Siemens No Glass 4.1 12.3 Yes total frost
47 ADB/Siemens No Glass 4.8 26.3 Yes total frost
48 ADB/Siemens No Glass 5.2 36.6 Yes donut signal partial
49 ADB/Siemens No Glass 5.5 43.7 Yes + glass donut
50 ADB/Siemens No Glass 6.6 78.5 No
51 Cegelec No 4.8 38.2 Yes (donut)
52 Cegelec No 5.2 51.5 No small 5 mm around
53 Crouse-Hinds No 3.4 2.2 Yes complete frost
54 Crouse-Hinds No 4.1 10.5 No
55 ADB/Siemens No Glass 4.8 28.6 No
78 ADB/Siemens Yes/Regula 5.5 70.6 Yes donut
79 ADB/Siemens Yes/Antifog 5.5 92.1 Yes donut

Minimum current test at -20°C

Test # PAPI Manufacturer Cover glass (Yes/No) RMS Current (Amp) Lens/glass Temperature (°C) Accumulation of frost (Yes/No)
80 ADB/Siemens Yes/Antifog 4.8 43.0 Yes
81 ADB/Siemens Yes/Antifog 5.2 60.5 Yes
82 ADB/Siemens Yes/Antifog 5.5 70.4 Yes
83 ADB/Siemens Yes/Antifog 6.6 115.8 Yes
84 ADB/Siemens Yes/Regular 5.5 58.4 Yes
85 ADB/Siemens Yes/Regular 6.6 96.5 Yes
86 ADB/Siemens Yes/Wired 5.5 55.6 Yes
87 ADB/Siemens Yes/Wired 6.6 91.3 Yes
88 ADB/Siemens No/Glass 6.6 61.1 Yes
89 Cegelec No 4.8 17.3 Yes
90 Cegelec No 5.2 29.9 Yes
91 Cegelec No 5.5 40.0 Yes
92 Cegelec No 6.6 71.5 Yes
93 ADB/Siemens No 4.8 29.2 No

Minimum current test at -30°C

Test # PAPI Manufacturer Cover glass (Yes/No) RMS Current (Amp) Lens/glass Temperature (°C) Accumulation of frost (Yes/No)
62 ADB/Siemens No 5.5 35.1 Yes
63 ADB/Siemens No 6.6 59.6 Yes
64 ADB/Siemens Yes/Antifog 5.5 63.5 Yes
65 ADB/Siemens Yes/Antifog 6.6 101.3 Yes (donut)
66 ADB/Siemens Yes/Regular 5.5 50.8 Yes
67 ADB/Siemens Yes/Regular 6.6 94.0 Yes (donut)
68 ADB/Siemens Yes/Wired 5.5 53.9 Yes (donut)
69 ADB/Siemens Yes/Wired 6.6 106.1 Yes (donut)
70 ADB/Siemens No 5.2 31.5 Yes
71 Cegelec No 5.5 29.2 Yes
72 Cegelec No 6.6 61.2 Yes
73 Crouse-Hinds No 4.1 -3.9 Low temperature
74 Crouse-Hinds No 4.8 10.5 Yes
75 Crouse-Hinds No 5.2 22.4 Yes
76 Crouse-Hinds No 5.5 32.1 Yes
77 Crouse-Hinds No 6.6 63.9 No

Defrosting test summary

Temperature PAPI -5°C -10°C -20°C -30°C
Crouse-Hinds Test #3
6 min.
Complete defrosting
Test # 30
9.30 min.
Complete signal, a
little frost on edge.
Test #99
6.5 min.
Small donut hole,
waterdrops,
complete signal.
(5113)
Test #13 – 8 min.
Test #58
15 min.
Light frost on top
section.
Cegelec Test #1
24 min.
Good signal
± 10 min.
Test #28
30 min.
Good signal
± 20 min.
Donut hole large.
Test #98
19 min.
Donut hole,
waterdrops,
complete signal
(5113)
Test #1 – 56 min.
Test #57
53.5 min.
Light signal ± 10 min/
Good signal ± 20 min/
Complete ±30 min.
Donut hole, poor
defrosting of lens
Siemens
No Glass
Test #2
22 min.
Total signal with
1 cm of ice around
lens on 5cm long
(Good signal
± 10 min)
Test #29
26 min.
Donut hole –
Complete signal.
Test #97
14 min.
Donut hole,
waterdrops,
complete signal.
(5113)
Test #14 – 30 min.
Test #56
30 min.
Donut hole – Signal
OK at ± 15 min.
Siemens
Regular
Test #6
32 min.
Donut hole –
Complete signal
around ± 20 min.
Test #33
17 min.
Complete signal –
Donut hole
Test #94
8 min.
Donut hole, water
drops, correction,
with cover glass,
complete signal
Test #59
10.10 min.
Donut hole, complete
signal.
Siemens
Wired
Test #4
32 min.
Good signal
± 20 min.
Donut hole
Test #31
9 min.
Donut hole,
complete signal.
Test #95
5 min.
Donut hole, water
drops, complete
signal
(5113)
Test #4 – 3 min.
Test #60
8.40 min.
Donut hole,
complete signal.
Siemens
Antifog
Test #5
32 min.
Good signal
± 10 min.
Donut hole
Test #32
18 min.
Large donut hole,
complete signal
Test #96
7 min.
Large donut hole,
complete signal
(5113)
Test #2 – 25 min.
Test #61
9.35 min.
Donut hole,
complete signal.

Note: Each cell contains test #, defrosting time at 6.6 Amp. and comments.

Minimum current test summary (partly defrosted)

This table contains minimum current test results where the ice on the lens/cover glass begins to melt. (A donut shape of ice remains around the lens)

Temperature PAPI -5°C -10°C -20°C -30°C
Crouse-Hinds Test #23
2.8 Amps
Complete frosting
2.8 no melting
1.4°C
Test #53
3.4 Amps
Complete frosting
no melting
2.2°C
Test #15
(5113)
4.1 Amps
No. ref.
8.1°C
Test #76
5.5 Amps
Complete frosting
and defrosting
32.1°C
Cegelec Test #25
3.4 Amps
Light frost melting
11.4°C
Test #57
4.8 Amps
Low signal ± 10min/
good signal ± 20min/
complete ± 30 min
Donut hole, poor
defrosting of lens.
38.2°C
Test #90
5.2 Amps
Small donut,
low signal
29.9°C
Test #72
6.6 Amps
Donut hole, low
signal
61.2°C
Siemens
No Glass
Test #20
3.4 Amps
Yes slowly
6.4°C
Test #48
5.2 Amps
Yes, donut hole,
partial signal
36.6°C
Test #19
5.2 Amps
Yes slowly
17.0°C
Test #63
6.6 Amps
Yes complete
frosting
No melting
59.6°C
Siemens
Regular
Test #8
3.4 Amps
Donut hole,
defrosting
16.3°C
Test #35
4.1 Amps
Donut hole
21.3°C
Test #84
5.5 Amps
Yes, donut hole with
water drops, low signal
58.4°C
Test #67
6.6 Amps
Donut hole,
water drops
94.0°C
Siemens
Wired
Test #12
2.8 Amps
Light frost, very
light melting
7.3°C
Test #41
4.1 Amps
Yes, donut hole
23.6°C
Test #86
5.5 Amps
Yes, donut hole, water
drops, low signal
55.6°C
Test #68
5.5 Amps
Yes, donut hole,
light frost
53.9°C
Siemens
Antifog
Test #10
2.8 Amps
Light frost, water
drops, defrosting,
donut
6.6°C
Test #38
4.1 Amps
Donut hole
28.5°C
Test #80
4.8 Amps
Yes, donut hole,
water drops
43.0°C
Test #64
5.5 Amps
Yes, light defrosting
63.5°C

Note: Each cell contains test #, minimum current, lens temperature and comments.

Minimum current test summary (fully defrosted)

This table contains minimum current test results where the ice on the lens/cover glass completely melts.

Temperature PAPI -5°C -10°C -20°C -30°C
Crouse-Hinds Test #26
3.4 Amps
6.4°C
Test #54
4.1 Amps
10.5°C
Test #17 (5113)
4.8 Amps
23.5°C
Test #77
6.6 Amps
Almost all clear,
very light frost on edge
63.9°C
Cegelec Test #27
4.1 Amps
22.5°C
Test #52
5.2 Amps
51.5°C
Test #92
4.8 Amps
No defrost
Large donut hole, water
drops, low signal
6.6 Amps – 71.5°C
(5113) Test #11
17.7°C
Test #72
6.6 Amps
No defrost
Donut hole, low signal
61.2°C
Siemens
No Glass
Test #55
4.8 Amps
28.6°C
Test #50
6.6 Amps
78.5°C
Test #88
6.6 Amps
No defrost
Yes, no donut hole,
very low signal
61.1°C
Test #63
6.6 Amps
No defrost
Yes, complete frosting
59.6°C
Siemens
Regular
Test #9
4.1 Amps
31.1°C
Test #37
6.6 Amps
94.5°C
Test #85
6.6 Amps
No defrost
Yes, donut hole with
water drops, low signal
96.5°C
Test #67
6.6 Amps
No defrost
Donut hole,
water drops
94.0°C
Siemens
Wired
Test #13
3.4 Amps
Donut hole
17.7°C
Test #45
6.6 Amps
102.3°C
Test #87
6.6 Amps
No defrost
Yes, donut hole, water
drops, low signal
91.3°C
Test #69
6.6 Amps
No defrost
Yes large donut hole,
light frost
106.1°C
Siemens
Antifog
Test #11
3.4 Amps
18.3°C
Test #40
6.6 Amps
116.9°C
Test #83
6.6 Amps
No defrost
Yes, donut hole,
water drops
115°C
(5113) Test #12
4.8 Amps – 7.2°C
Test #65
6.6 Amps
No defrost
Yes, donut hole
101.3°C

Conclusions

Defrosting Tests:

Most of the PAPI took a longer time to defrost at -5°C and -10°C than at -20°C. This can be explained by the type of ice. At -5°C and -10°C, the ice is clear, at -20 °C, the ice is white.

The best average performance was achieved by Crouse-Hinds PAPI.

The best defrosting time was achieved by Siemens PAPI with wired cover glass at -20°C in 5 minutes.

The most energy efficient PAPI is the Crouse-Hinds.

Minimum Current Tests:

What was simulated during this test is a snow storm or ice storm depending on test temperature, on a PAPI already energized. We obtained three types of results: The ice is not melting at all, the lens defrosts partially or the lens defrosts instantly.

We did two summary tables (completely and partly defrosted) because even if the lense is partly defrosted, the signal can be considered complete based on our criteria. It is to be noted that even if we consider the signal to be complete during the tests at 12' from the receiving panel, it does not necessarily means that the signal will be complete in the "real world" (at 1 mile).

Only Crouse-Hinds PAPI can meet the completely clear lens requirement at every temperature that we tested.

Siemens and Cegelec PAPI can meet the completely defrosted lenses at temperature above -10°C. At temperature below -10°C, there is always ice remaining on the edges of the lenses.

For partly defrosted lenses, the minimum current vary from 5.5 Amps to 6.6 Amps at -30°C.

Recommendations

We recommend that other tests in the field be made to confirm the above conclusions which would also consider other parameters, such as the cooling effect of the wind, the effect of the sun on the observation of the output signal from distances greater than the 12 foot laboratory distance, the "real world" frost deposit thickness and deposit rate of, as well as other meterological conditions. We also need to establish a scientific way of calculating the degradation of the PAPI to what would be considered as a false signal, from a true signal.

Based on these tests results, the PAPI must be energized at least 53.5 minutes before any airplane landing or remain energized at 6.6 Amp at all time.