[PEREZGONZALEZ Jose D et al [eds] (2013). Ab-initio pilots' performance using T-VASIS versus PAPI. Knowledge (ISSN 2324-1624), 2013, pages 94-96.] [DOI] [Printer friendly]
T-VASIS versus PAPI
Lewis (20111) compared the accuracy with which a group of ab-initio pilots tracked the correct approach-to-landing glide path when using two different approach lighting systems (T-VASIS4 and PAPI5). Results (see illustration 1) show that pilots were better at tracking the correct glide slope in 8 scenarios out of 10 when using T-VASIS and in 2 scenarios out of 10 when using PAPI. On average, ab-initio pilots performed better with T-VASIS (mean difference = 6), a sensible difference of moderate magnitude (when attending to the unstandardized effect size).
|Illustration 1. Average deviation from glide slope*|
|Unstandardized effect size3||small||2||medium||6||large||9|
|(* Angular deviation from 0, multiplied by 100)|
When questioned about their perception of fit-for-purpose and preference for one lighting system or the other, most pilots perceived T-VASIS as being a better visual system when flying on the glide slope or when above it, but perceived PAPI as being a better visual system when flying below the glide slope. Irrespective of perception, though, most preferred PAPI over T-VASIS.
|Illustration 2. Assessment of best-fit-for-purpose and preference for approach lighting system|
|Number (%) of pilots who think best displays when||Number (%) of pilots|
|On glide slope||Above glide slope||Below glide slope||Who prefer|
|PAPI||6 (42%)||3 (21%)||8 (57%)||9 (55%)|
|T-VASIS||8 (57%)||11 (79%)||6 (43%)||5 (35%)|
Want to know more?
- LEWIS (2011) original article
- The original article provides full detail about the research.
- Skybrary - VASIS
- This Skybrary page offers a small introduction to different visual approach slope indicators (such as T-VASIS and PAPI).