June 27, 2014

A Refrigerator Moment

This video has been making the rounds lately. 

It concerns a Harrier landing on a assault ship without the benefit of the planes nose landing gear.


This is pretty interesting but there is one thing that concerns me.
The stand, is not extemporized. It is mentioned offhandedly to be something they have for just such an occasion.This indicates that the forward landing gear malfunctions enough that the nose stand is part of their regular deck equipment. This does not inspire confidence. 

UPDATE: John Spencer explains in the comments that the stands are, in fact, dual use. 

Posted by: The Brickmuppet at 09:01 AM | Comments (14) | Add Comment
Post contains 99 words, total size 1 kb.

1

He sure came down hard, though not hard enough to seriously damage the airframe, I guess.

My bet is that he was running out of water. Harriers only carry enough water to run in hover mode for 90 seconds, and it looks like he was pushing the limit.

But your point is well taken, too. That thing is a deliberate design and standard deck equipment? Yikes!

Posted by: Steven Den Beste at Fri Jun 27 14:59:31 2014 (+rSRq)

2 It would also be handy in case of combat damage.  For conventional warplanes, they erect crash barriers on the runway if they don't think they can land and stop normally.  For Harriers, they have "landing stools"...

Posted by: Siergen at Fri Jun 27 16:59:39 2014 (8/vFI)

3 The stands are used for maintenance on the plane when it is required that the forward landing gear needs to not touch the deck. There are similar mounts for replacing the other landing gear too. It / they are just fancy jack stands.

Posted by: jon spencer at Fri Jun 27 19:24:23 2014 (JSYPT)

4 Harriers only carry enough water to run in hover mode for 90 seconds...

Wait, what?  Can you explain, Steven?

Posted by: Wonderduck at Fri Jun 27 23:49:10 2014 (DiS7r)

5

When they are hovering, there are gizmos that vector thrust from the engine straight down. But the engines don't produce enough thrust normally to hold the jet up. So they overdrive the engines by injecting water.

It's the same principle as water injection in WWII piston engine fighters. The water cools the air flow, which permits more air and more fuel to pass through the jet engine, producing more thrust. But they have to use a lot of water to get that effect, and they don't carry all that much because water is heavy.

It turns out that they carry enough for 90 seconds of hover. (And too bad for Arnold in True Lies.)

Posted by: Steven Den Beste at Sat Jun 28 00:36:09 2014 (+rSRq)

6 From here:

The maximum take-off thrust available from the Pegasus engine is limited, particularly at the higher ambient temperatures, by the turbine blade temperature. As this temperature cannot reliably be measured, the operating limits are determined by jet pipe temperature. To enable the engine speed and hence thrust to be increased for take-off, water is sprayed into the combustion chamber and turbine to keep the blade temperature down to an acceptable level.

Water for the injection system is contained in a tank located between the bifurcated section of the rear (hot) exhaust duct. The tank contains up to 500lb (227kg, 50 imperial gallons) of distilled water. Water flow rate for the required turbine temperature reduction is approximately 35gpm (imperial gallons per minute) for a maximum duration of approximately 90 seconds. The quantity of water carried is sufficient for and appropriate to the particular operational role of the aircraft.

Posted by: Steven Den Beste at Sat Jun 28 00:41:36 2014 (+rSRq)

7 So it turns out I got the detail wrong, but the overall fact was still right.

Posted by: Steven Den Beste at Sat Jun 28 00:43:01 2014 (+rSRq)

8 I've seen Harriers hover at airshows for longer than 90 seconds, so I suspect that limitation is for when the aircraft is fully loaded with ordnance and fuel.

Posted by: Siergen at Sat Jun 28 08:57:30 2014 (8/vFI)

9 Did you actually time it? Subjective evaluations of duration of extraordinary and noteworthy events are notoriously imprecise and tend to be on the high side. (I think the principle was called "All eclipses last five minutes" because subjectively it seems that way even if totality was actually shorter than that.)

Posted by: Steven Den Beste at Sat Jun 28 09:15:41 2014 (+rSRq)

10 The numbers seem slightly off, given "A Pint's a Pound the whole world 'round." A Gallon of water is typically 8 lbs. (and a Gallon of Gasoline is typically around 6.  Not sure about Diesel/Jet A).

Posted by: Mauser at Sun Jun 29 01:21:08 2014 (TJ7ih)

11 A pint of water weighs a pound and a quarter.  :p

Except in the US, Liberia, and February.

Posted by: Pixy Misa at Sun Jun 29 04:24:52 2014 (PiXy!)

12 Pixy, we can't help that the Imperial standards were diddled by Parliamentary souses determined to squeeze four extra fluid ounces into their beer measures, can we?  The old measures continued as they ever were, here in the rebelled provinces.

Posted by: Mitch H. at Mon Jun 30 15:36:29 2014 (jwKxK)

13 According to The Blaze, a previous attempt to land on a stack of mattresses did not end quite well, after which the stool was constructed.

Posted by: Pete Zaitcev at Mon Jun 30 20:26:06 2014 (RqRa5)

14 Hah! Thanks for that Pete. I'm surprised it didn't result in a Blaze. Yes, yes I think the Leathernecks are right and the stool is superior. 

Posted by: The Brickmuppet at Mon Jun 30 21:19:53 2014 (DnAJl)

Hide Comments | Add Comment

Comments are disabled.
30kb generated in CPU 0.02, elapsed 0.0277 seconds.
66 queries taking 0.0132 seconds, 277 records returned.
Powered by Minx 1.1.6c-pink.