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When vertically landing, do Harrier pilots cut power before they touch the ground?

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    $\begingroup$ Well, they obviously have to at least reduce power, otherwise they could bounce back up, due to backblast from the ground. The same power which makes you lose altitude at 10 meters might make you hover or even gain altitude at 0.5 meters. $\endgroup$
    – vsz
    Jun 2, 2019 at 11:08
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    $\begingroup$ Based on this comment you left, you have not provided the research that you simply want to confirm (you're not accepting any different answer it seems). Please include the relevant research in the question body, otherwise it's unclear what you're asking, thanks. $\endgroup$
    – user14897
    Jun 2, 2019 at 14:23
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    $\begingroup$ On the carrier I imagine the deck is always rocking up and down in the 1-2 meter range. So it's pretty dangerous to stay at that height for too long, might as well slam it. It's more or less like landing a helicopter on a ship I guess. $\endgroup$
    – user3528438
    Jun 2, 2019 at 21:08

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The Harrier's NATOPS flight manual (A1-AV8BB-NFM-000) is available online.

Both the text and the diagram in Part III Normal Procedures confirm the opposite. Thrust is idled when "positively down". And not before. Which agrees with the dozens of soft landing videos on YouTube (base and shipboard alike). And as with shipborne helicopters, in rough seas the pilots wait for the pitching deck to catch up to them. Anything else would be an unlucky situation the pilot has found themselves in, but is not standard procedure.

7.6.4 Vertical Landing

(...)

When positively down:

  1. Throttle — IDLE.
  2. Brakes — APPLY.
  3. Nozzles — AFT.
  4. Trim — 4° ND.
  5. Water — OFF (if selected).

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Moreover, before step 5 there is this note:

If strakes or gun pods are not installed some suck-down effect is present.
A power increase may be required near touchdown to prevent excessive sink rate.

The only mention of idling (i.e., cutting/chopping) is step 5 and the diagram.

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  • $\begingroup$ I would call this selectively choosing misleading information. See the rest of the paragraph you quoted - I included it in my answer below. (You omitted steps 1-4) $\endgroup$
    – jwzumwalt
    Jun 4, 2019 at 16:40
  • $\begingroup$ @jwzumwalt: "Some reduction" does not equal cut/chop. Cut means idle. You have actually omitted the only relevant – regarding cut/chop – step which is 5 (and the diagram). So who's being selective? $\endgroup$
    – user14897
    Jun 4, 2019 at 17:41
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Cutting the power just before touchdown in VTOL aircraft appears to be appropriate in certain circumstances. After watching 20-30 landings on Utube most where soft landings. However two landings on pitching ship decks appear to show the airplane's decent increase within a few feet of the ground consistent with the power being cut while in the air. 2:15 and 0:25

Not mentioned in the information below is the reduction of FOD and the tendency for the Harrier to spall and break up concrete in just a few seconds. - J. Zumwalt

enter image description here [ From the Harrier manual - information omitted before the quoted paragraph given by YMB1 ]

Yes, Harrier pilots are known for ‘slamming’ their jets on the ground by cutting power in the last few feet. In fact, for a Harrier, a smooth landing is a scary landing.

The reason pilots cut the engines a few feet from the ground are primarily two:

1) To kill the high potential energy stored in the craft while it is hovering and prevent it from turning into kinetic energy which may render the craft uncontrollable. When the harrier is hovering in the air, the engines are working at a high power setting. The complete weight of the aircraft is thus balanced by the engines alone, since the lift component from the airfoil (wings) while hovering is zero.

2) To prevent the extremely hot jet blast from bouncing off the ground and getting sucked into the engine again, thereby damaging the engine.

-Sagar Dhawan

They do cut power a few feet above deck, especially if the carrier is in rough water.

If the VTOL (F-35 included) carried full power landing onto the deck, the LG will take on some weight, and instantly the plane is overpowered and tends to rise up. The engine cannot spool down quick enough in that instance to prevent this “inadvertent takeoff”.

This condition is worsened in bad weather, as the deck is also moving up and down. So if the plane has full power on the way down and the deck is moving up, it will be thrust up into the air, possibly out of control.

So, it is best to cut power a few feet up so the plane sticks the landing and stays safely on deck while the engine goes to idle. And for a moving deck, pilots train for it, all a matter of timing.

The LG is designed for such “heavy landings”. - Joel Berson[

Harriers will drift side to side if the pilots sit hovering close to the ground for too long. It has Caused accidents in the past. So once the pilot is confident in his approach, they reduce power to mitigate the length of time in the zone where they may drift sideways because of the thrust rebound. - Megan Portero

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    $\begingroup$ It doesn't make sense as slamming it down may risk a bounce and a roll. I don't know who those people are, but anyone can claim to be anyone on Quora and the internet in general. Their argument simply confirms the question which does not provide evidence, and which you simply copied over here. $\endgroup$
    – user14897
    Jun 2, 2019 at 15:10
  • $\begingroup$ The sound in both videos is consistent with the pitching deck catching up to the planes, then thrust was idled. $\endgroup$
    – user14897
    Jun 4, 2019 at 1:44
  • $\begingroup$ Your discounting the 100-200ms sound travels in 100-200ft to the photographer AND turbine inertia that lags several seconds behind a change in throttle. There is also no way of knowing how close the audio is synced to the video. Both aircraft do drop the last few feet. $\endgroup$
    – jwzumwalt
    Jun 4, 2019 at 1:48
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    $\begingroup$ If there's no way of knowing, then equally it's not evidence for either case. Especially as you wrote, dozens of videos show soft landings, despite what the question says(!). All I'm reading is confirmation bias. If my observations aren't helpful, then let's agree to disagree. $\endgroup$
    – user14897
    Jun 4, 2019 at 1:54
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    $\begingroup$ "Sometimes" can be a valid answer. It does not have to be "always" or "never" :) $\endgroup$
    – jwzumwalt
    Jun 4, 2019 at 2:03
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Also from The Jet Engine issue 5 page 85

Just to add a bit to the difference of opinion in some of the answers above, an excerpt from The Jet Engine issue 5 by Rolls Royce, page 85 about STOVL aircraft with thrust vectoring nozzles:

Particular performance issues raised by this include the potential for hot exhaust gases to enter the intake - potentially leading to surge or stall - and the need for the engine to decelerate rapidly on landing. This requirement for a rapid deceleration is because, on a constant velocity vertical descent, engine thrust equals aircraft weight, and so when the aircraft lands it will tend to bounce and then rise at a similar rate.

And the punchline:

Thrust has to be quickly reduced to prevent this, leading to potential surge of the low-pressure compressor.

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They don’t. If you watch carefully they set power for a gentle descent around 1-2 ft/s then pull power to idle on impact with the deck. Cutting power in a vertical landing prior to touchdown either results in a really firm touchdown and possibly damage to the landing gear or airframe, depending on how high the pilot is prior to touchdown.

Landing a Harrier in s conventional manner on a runway is possible. The aircraft handling much like any other high performance fighter in the roundout.

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  • $\begingroup$ For the media component: youtu.be/NNhyF1DHWjc?t=62 $\endgroup$
    – user14897
    Jun 1, 2019 at 23:32
  • $\begingroup$ Actually, they do. I found an answer by a Harrier Pilot on the Quorum forum. The correct answer is very interesting. In the pilots explanation, a "soft" landing is considered a "bad" landing and gives a very good explanation. $\endgroup$
    – jwzumwalt
    Jun 2, 2019 at 5:31
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    $\begingroup$ @jwzumwalt, have a link to that particular question/answer? Seems relevant to include that in this discussion :). $\endgroup$
    – Bram
    Jun 2, 2019 at 8:40
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    $\begingroup$ Well a 1-2 ft/s is hardly a soft landing. I agree that they want to plant it, but they are not cutting power until they make contact with the deck. $\endgroup$
    – Carlo Felicione
    Jun 2, 2019 at 13:17
  • $\begingroup$ @Bram: I agree, it should have been provided as research in the question body, and Carlo's answer agrees 100% with the video I linked; anyone can claim to be anyone on the internet after all. $\endgroup$
    – user14897
    Jun 2, 2019 at 14:14

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