Results 1 to 9 of 9

Thread: Definition of non-certified instruments

  1. #1

    TWOT


    76th vFS Squadron Command
    Oliver's Avatar
    Netherlands
       Netherlands
    Join Date
    Jun 2015
    Posts
    2,333

    Awards Showcase

    Thanks Thanks Given 
    560
    Thanks Thanks Received 
    878
    Thanked in
    532 Posts

    Definition of non-certified instruments

    In our study material one or more instruments (the HUD being one off the top of my head) are described as non-certified instruments. What does that mean? Apart from the obvious explanation that it lacks certification...

    I am flying an aircraft, it offers several tools to help me flying and navigating. If one of these tools is not certified, does it mean it is not reliable or accurate (enough)? What purpose would it serve if that's the case?

    The main reason I ask is because the study material as well as my instructor(s) emphasized using the instruments, at least during IFR procedures. But I find myself in numerous situations where the HUD is so much more convenient to use from a multi-tasking perspective. For instance I would hate to see my TVV gone, having to continuously monitor the Altimeter and the VVI to remain in level flight or to land.

  2. #2
    Member Dojo's Avatar
    United States
       United States
    Join Date
    May 2014
    Posts
    2,246

    Awards Showcase

    Thanks Thanks Given 
    1,894
    Thanks Thanks Received 
    1,671
    Thanked in
    800 Posts
    There's a lot of generic speak here. First, what study material specifically are you referring to? What page, line, section?

    The HUD, in the A-10 specifically, is referred to as not being certified for IFR. That is, specifically in the A-10C, you don't use the HUD for an IFR procedure. Whereas, in the F-18 (as an example), the HUD is certified for IFR.

    As an example, in the A-10C, your head should be down referencing the gauges for an IFR departure or approach. The HUD shouldn't be used at all.

    The systems used in IFR (TACAN, ILS, etc) render their output on the ADI and HSI, not on the HUD in the A-10C. In an F18, The ILS glide path and localizer are rendered on the HUD.
    Last edited by Dojo; 02Feb16 at 18:44.

  3. #3

    TWOT


    76th vFS Squadron Command
    Oliver's Avatar
    Netherlands
       Netherlands
    Join Date
    Jun 2015
    Posts
    2,333

    Awards Showcase

    Thanks Thanks Given 
    560
    Thanks Thanks Received 
    878
    Thanked in
    532 Posts
    Quote Originally Posted by Dojo View Post
    The HUD specifically, in the A-10 specifically, is referred to as not being certified for IFR. That is, specifically in the A-10C, you don't use the HUD for an IFR procedure. Whereas, in the F-18 (as en example), the HUD is certified for IFR.

    As an example, in the A-10C, your head should be down referencing the gauges for an IFR departure or approach. The HUD shouldn't be used at all.
    This is what I mean, what does not certified mean? Is the information it is giving not accurate enough? Or is the chance of errors given by the HUD larger than with other instruments?

    I know I shouldn't use the HUD in the situation you describe and I'm not saying I want to or I do, but my question is why? I don't understand the concept of an instrument which is not certified.

    I would have to look for exact quotes if my question alone is not sufficient to express what I mean.

  4. #4
    Member Dojo's Avatar
    United States
       United States
    Join Date
    May 2014
    Posts
    2,246

    Awards Showcase

    Thanks Thanks Given 
    1,894
    Thanks Thanks Received 
    1,671
    Thanked in
    800 Posts
    I was more interested in what other instruments. You seem to generically be asking about certification, I wanted to know what other instruments besides the HUD.

    Essentially, the HUD can't be used to fly the procedure correctly. You're saying the HUD is a tool for convenience, but that tool, in the A-10, doesn't have the information you need to fly the procedure.

    For example, you're doing the OBORA1 departure. You have to fly 8nm from the TACAN. Where on the HUD is the TACAN distance?

    Now you're doing the Vaziani HI-ILS approach. You need to pick up the glide slope. Where on the HUD is the glide slope? So it's not a matter of the general reliability or accuracy of the HUD, the HUD in the A-10 doesn't have the information you need to actually be able to fly the IFR procedure according to the chart.

    In other aircraft, again, like an F-18, those systems output to the HUD, therefore the HUD can be used.
    Last edited by Dojo; 02Feb16 at 18:52.

  5. The Following User Says Thank You to Dojo For This Useful Post:

    Oliver (02Feb16)

  6. #5

    TWOT


    76th vFS Squadron Command
    Oliver's Avatar
    Netherlands
       Netherlands
    Join Date
    Jun 2015
    Posts
    2,333

    Awards Showcase

    Thanks Thanks Given 
    560
    Thanks Thanks Received 
    878
    Thanked in
    532 Posts
    Regarding other instruments, I wasn't sure about them but I thought I recall there were others besides the HUD that are not certified. Maybe I'm wrong and that caused some confusion in my post so let's forget about that and focus only on the HUD of the A-10C as that is definitely described as not certified.

    You're right that the A-10C HUD is lacking info required for an IFR departure/arrival procedure. It's just that the term not certified makes it sound like not qualified, or not trusted to be used for something. At least, that's what I made of "not certified".

    Maybe it's the difference in language, something not certified in Dutch means it is not yet proven to be safe, IOW you're taking a risk when you use it.
    Last edited by Oliver; 02Feb16 at 19:02.

  7. #6
    In my experience the HUD is categorized as a secondary instrument. Only primary instruments e.g. altimeter can be relied upon for IFR. The issue with the HUD is that in the real world it is susceptible to lag, and that is why it is not to be relied upon.

    I'm sure that Baxter or Noodle can respond far more authoritatively and detailed on this topic than i can.

  8. #7
    Retired pilot Ski's Avatar
    United States
       United States
    Join Date
    Apr 2014
    Posts
    726

    Awards Showcase

    Thanks Thanks Given 
    1,415
    Thanks Thanks Received 
    233
    Thanked in
    174 Posts
    It is a great question Oliver. From what I gather, a certified instrument is one that is 100% trustworthy during flight and an uncertified instrument is one that is not to relied upon 100%. If you were to lose your HUD (not certified) during flight, you could rely on other "certified" (reliable) instruments to get you home. If you lost your HSI, SAI, fur guages, VVI, Airspeed indicator, etc. (certified), you'd have no idea which way you would need to go to get home. I hope that helps and if I'm wrong, someone please correct me.

  9. #8
    GOMER 2 Noodle's Avatar
    United States
       United States
    Join Date
    Mar 2012
    Posts
    1,572

    Awards Showcase

    Thanks Thanks Given 
    606
    Thanks Thanks Received 
    1,947
    Thanked in
    682 Posts
    Oliver,

    The definition you offer above is accurate. The HUD has not been tested and proven reliable enough to certify it as a primary reference during instrument flight. Although I don't know the specific reason in this case, the reason for lack of certification usually comes down to one of a few things:

    1) Money. There are many ops limits and restrictions in any aircraft's flight manual which are driven primarily by the fact that a given configuration, condition, or operation was not economically feasible to flight test. Stores configurations and flight envelopes are usually good examples of this. The envelope simply stops where the flight test program ran out of money and sorties to expand it further.

    2) Reliability. There are requirements regarding redundancy and reliability of components in order to certify them for certain operations. There are volumes of mil-spec and mil-std requirements, and it may be that in order to certify a component for instrument flight, it must have a mean time between failure of X hours, or it must not have a failure mode which would allow it to display invalid data, etc.

    Personally, I think it's the latter. Primary flight instruments are required to display a flag when input or output data is interrupted or invalid. The HUD does not do this. There are conditions in which attitude data may be invalid, but the HUD will not notify the pilot of this, thus it is unsafe to use as a primary reference. It might also be that the HUD has a single point of failure, meaning that a single failure of a sub-component could render the HUD inoperable; not good when there are no indications of a failure...

    The HUD is a great tool and is very reliable, but the only way to know it's malfunctioning is by comparing it what you see outside the canopy. Obviously, this isn't possible during flight in instrument conditions.

  10. The Following 7 Users Say Thank You to Noodle For This Useful Post:

    Baxter (02Feb16), IronHog (02Feb16), Kimi (03Feb16), Oliver (02Feb16), Ski (02Feb16), Snoopy (03Feb16), Toneking (02Feb16)

  11. #9

    TWOT


    76th vFS Squadron Command
    Oliver's Avatar
    Netherlands
       Netherlands
    Join Date
    Jun 2015
    Posts
    2,333

    Awards Showcase

    Thanks Thanks Given 
    560
    Thanks Thanks Received 
    878
    Thanked in
    532 Posts
    Thanks for the clarification.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  


Like our website?

You can help us by donating to cover our costs.

Many sincere thanks!


Search

Follow us

Twitter Twitter youtube iTunes Subscribe to our Podcast