HUD goes Tango-Uniform. Do you RTB?

[ExRAFRadar]

On another post Beagle mentioned this about a glass cockpit, in the context of a tail chase:

With all that gucci glass, will Bloggs be spending longer time 'head-in' than was accepted in aircraft such as the Bulldog or JP? Made me wonder that with all the Gucci (love that word, sorry) helmets and HUD's if you lose the electronics in either would a modern FJ pilot be forced to abort the mission?

In other words have the days of Stop Watches and Charts long gone in modern Fast Jet fleets?

[MSOCS]

It depends on what it is you are doing; the phase of the mission and its importance.

Most FJ HUDs are not the primary flight reference so it isn't an essential item. It could just be the projection system and a "HUD" display could be available on head-down display.

There are lots of considerations and eventualities however if you could get the aircraft back on the ground and fixed for the next sortie quickly then it may be the best course of action.

[Pontius Navigator]

To add to MSOCS, in WW2, pressing on and unloading your bombs in the target area was seen as essential to the aim. If you and your aircraft perished in the event then there were more to follow you.

Today, if your system is degraded to the extent that you might miss the target then the correct thing to do is RTB. If your weapons are needed for effect, hit or miss, then pressing on might still make sense.

Better by far though not to risk your scarce airframe for a miss.

During one cold war mission we experienced a number of lightning strikes; our option was to clear the area and may be RTB or press on. We pressed on.

[Easy Street]

In other words have the days of Stop Watches and Charts long gone in modern Fast Jet fleets?

For all practical purposes, yes. In the 80s and 90s (and in some circles into the 2000s) map and stopwatch lived on as the back-up to inertial navigation. Nowadays inertial navigation is itself the back-up system to GPS or terrain profile matching, and we don't need to waste much time on the back-up to a back-up! All of the MDR associated with map and stopwatch is still used to cross-check the numbers churned out by the computers (for time, drift, fuel etc) but actual map-work itself? Not so much.

Losing a HUD and HMS would not have any significant effect on the safe operation and navigation of the aircraft - as stated by others, flight safety-critical functions are backed up elsewhere. However it could entirely remove the ability to aim guns or visual air-to-air missile shots and would probably force the pilot to spend an unhealthy amount of time looking at heads-down displays for tactical information. It is this effect on mission capability, rather than any effect on the basic aspects of flying, that would be most likely to handicap an aircraft suffering display failures.

[safetypee]

Lightning Battle Flight launched from GUT for live missile firing at Aberporth.
Radar fails en-route, then LFS (poor HUD) fails when on the range.
Chinagraph pencil ‘aiming’ cross placed on centre windscreen; aircraft and missile pointed at the target, acquisition, fire, live warhead success.
Return via Valley with bottle and 200 (always kept under Battle Flight seats) – HM customs notified via ‘Jones the plod’, but the aircraft was always in a restricted area.
Train as you are going to flight – fight as you train.

[MSOCS]

Safetypee,

That get-around clearly worked in its time however - and to use your example - in the age of BVR and HOBS missile profiles it would be a brave and stupid pilot to do such a thing on a training sortie nowadays. Indeed, I'd rip them a new one in the debrief. As I intimated earlier, the context of the mission and its imperative drives the risk you need to take but one must always ask whether it is within one's gift to take it or elevate it in the first place.

That said, thanks for sharing your WIWOL experience!

[Courtney Mil]

Most FJ HUDs are not the primary flight reference

Not true. These days the HUD is the primary flight reference, but with good heads down instruments the loss of the HUD isn't an impediment to safe flight. Weapons aiming, etc is another matter.

[ExRAFRadar]

What would this chap do if he's helmet goes U/S ?

F35 Helmet at RAF Boscombe Down | Latest News from Helmet Integrated Systems Ltd (http://www.helmets.co.uk/news/f35-helmet-at-raf-boscombe-down)

I suppose he could eject and scare the enemy to death.

[MSOCS]

CM,

Sorry. My understanding is that certification of a HUD as a PFR, to the demanded SIL, is very rare. HD Insts are more easily PFR compliant as far as standards are concerned for flight critical functions, therefore most FJ have a note in their RtS stating such.

The fact that aircrew spend 99% of their sortie time using the HUD (i.e "primarily" using it) is another matter.

[LOMCEVAK]

I believe that the first UK Military aircraft to have the HUD certificated as the primary flight display was the Sea Harrier FA2. Anyone like to confirm that?

[Lionel Lion]

If it fails in my 787-9 you just ask the lovely red wearing cabin crew for another cup of tea :)

[Pontius Navigator]

Lionel, that opens a different can of worms. Flown in the 787 twice, loved it.

[Engines]

LOM,

I can confirm that. The FA2 HUD was assessed by Boscombe Down to be carrying 'primary flight display information' quite late on in its test programme. First one as far as I am aware, but happy to be corrected.

BD then recommended a (highly expensive) programme of software analysis, which the MoD agreed to fund. After 6 months (having spent most of the dosh) they reported that they couldn't carry out any software analysis.

Great result - not.

Military aircraft cockpit display design (and certification) is one of those somewhat arcane areas where each major country has its own rather firmly held set of standards, opinions (or prejudices - take yer pick), over which fairly endless discussions can be held. In some cases, influential test pilots with strongly held opinions can be, well, influential. Add in the known fact that asking five pilots any question results in at least 6 answers can make delivering an 'acceptable' cockpit a bit of a saga.

As far as I know, HUDs have been classed as primary flight displays for some years now.

Happy New Year to all those sorting out the displays,

Engines

[GTPerformer]

The Typhoon HUD is Class 1 software for the majority of the primary flight reference symbology, hence guaranteed integrity, with no need to cross reference.

If the system detects errors (within tolerances) a computer handover occurs, if the errors continue, the symbology will occult, a warning given to the pilot, which then requires the use of other displays. (MHDs or GUHs)

This was the first of its kind (and may still be) and a customer requirement (CM may know more) which was an unknown at the time, however through lots of hard work and testing became a reality.

Unsure if there are any other Class 1 HUD/HMDs now in use.

GTP

[Courtney Mil]

The fact that aircrew spend 99% of their sortie time using the HUD (i.e "primarily" using it) is another matter.

Again, no. The HUD is certified and taught as the primary flight instrument. This was/is the case for Tornado F3, F-15, Typhoon and Rafale - to my knowledge. I would be surprised if it were different on any other recent/current type. HUDs are designed with the intention of being the primary flight instrument. There would be no point in putting all the important stuff - attitude, heading, nav info, airspeed, altitude, ROC/D, etc, if it wasn't certified for use.

[Just This Once...]

I don't recall the Tornado HUD (all marks) ever being cleared as the primary flight reference and given where we are with DAL I would be surprised if the RTS changed, even for the GR4.

[MSOCS]

Again, more than happy to be educated on this but my understanding is that Typhoon is the only UK FJ with the required assurances that GTPerformer covered very eloquently in his post.

[Mogwi]

HUD failure robbed me of my fifth kill in'82; both missiles fired (successfully) and only guns remaining. Wasn't good at no-HUD, hi-deflection shot; guess I should have practised more with my 12-bore!

Swing the lamp!

[overstress]

f it fails in my 787-9 you just ask the lovely red wearing cabin crew for another cup of tea

Like the one in the middle?

https://metrouk2.files.wordpress.com/2013/05/ay_109685748.jpg

[AutoBit]

I vaguely remember something from my IRE ground school that the HUD on the Harrier (GR7/9) couldn't be classified as the PFR as it didn't have an electrical back up. Single engine, single gen if you lost AC power you lost the HUD (same with an MC fail), hence the restriction in the RTS. MSOCS is that correct?

Mogwi - Awesome post!!!

[NutLoose]

Didn't the Jag have a plastic clip on for the HUD in a stowage on the left cockpit wall that gave a sort of manual back up aiming system.

[MSOCS]

Autobit, I too vaguely remember a keen IRE mentioning such a thing on the Harrier years ago, now you come to mention it.

[Courtney Mil]

Single engine, single gen if you lost AC power you lost the HUD (same with an MC fail), hence the restriction in the RTS

HUD goes blank, use main instrument panel gauges. They fail use stby instruments. They fail...

When were standard instruments not certified because they might fail leading to use of stby instruments?

Now the fallback goes straight from HUD to "peanut gauges". The conventional instruments take time to call up on the MFDs if you're using them for other purposes.

[AutoBit]

CM,

I feel we may be going around in circles here. Im not disagreeing with your logic. What you describe is exactly how we flew, but if my memory is correct the HUD was not the PFR for the reasons numerous people have attempted to describe, until Typhoon.

[oldmansquipper]

I recall my first back seat trip in the mighty Jaguar out of Laugh`in Laarbruch (Mid 70s) at about V1, the NAVWASS suddenly displayed the big green cross of doom.

We continued on our way (I hesitate to say `continued in the climb`, cos it was a hot day and we were in an early Jag) but the road traffic lights at Well were on red, so that was a bonus.

As things stabilised I said to my chauffeur (a Mr Phil Fl*nt) "so what happens now then?"

He said nothing but held up a quarter mil marked up with chinagraph lines, and waved it at the stop watch. I got the message quickly as this was the primary navigation system I was used to in my glider! Fair enough.

The trip then went very well IMHO and included the 450kts down the Mosel looking up at the vineyards .. Awsome:D

Not much changes!;)

[Courtney Mil]

CM,

I feel we may be going around in circles here. Im not disagreeing with your logic. What you describe is exactly how we flew, but if my memory is correct the HUD was not the PFR for the reasons numerous people have attempted to describe, until Typhoon.

No, not at all. I wasn't disagreeing with you. I was just comparing the logic of the day, the new-fangled HUD as a flight instrument versus the received wisdom of the main instrument panel.

New ideas (as the HUD was then) sometimes hit dire opposition - it seems the safety guys sometimes fear the change that operators find really good.